在阅读了各种文章后，我想通了。
以下是步骤。
$rvm get head
$rvm --force 2.0.0
$gem update
$gem install rails
顺利通过。
以下是输出：
Saads-Mac-Pro:~ SMD$ gem install rails
Building native extensions. This could take a while...
/Users/SMD/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/site_ruby/2.0.0/rubygems/ext/builder.rb:54: warning: Insecure world writable dir /usr in PATH, mode 040777
Successfully installed atomic-1.1.13
Fetching: thread_safe-0.1.2.gem (100%)
Successfully installed thread_safe-0.1.2
Fetching: activesupport-4.0.0.gem (100%)
Successfully installed activesupport-4.0.0
Fetching: builder-3.1.4.gem (100%)
Successfully installed builder-3.1.4
Fetching: rack-1.5.2.gem (100%)
Successfully installed rack-1.5.2
Fetching: rack-test-0.6.2.gem (100%)
Successfully installed rack-test-0.6.2
Fetching: erubis-2.7.0.gem (100%)
Successfully installed erubis-2.7.0
Fetching: actionpack-4.0.0.gem (100%)
Successfully installed actionpack-4.0.0
Fetching: activemodel-4.0.0.gem (100%)
Successfully installed activemodel-4.0.0
Fetching: arel-4.0.0.gem (100%)
Successfully installed arel-4.0.0
Fetching: activerecord-deprecated_finders-1.0.3.gem (100%)
Successfully installed activerecord-deprecated_finders-1.0.3
Fetching: activerecord-4.0.0.gem (100%)
Successfully installed activerecord-4.0.0
Fetching: mime-types-1.24.gem (100%)
Successfully installed mime-types-1.24
Fetching: polyglot-0.3.3.gem (100%)
Successfully installed polyglot-0.3.3
Fetching: treetop-1.4.15.gem (100%)
Successfully installed treetop-1.4.15
Fetching: mail-2.5.4.gem (100%)
Successfully installed mail-2.5.4
Fetching: actionmailer-4.0.0.gem (100%)
Successfully installed actionmailer-4.0.0
Fetching: thor-0.18.1.gem (100%)
Successfully installed thor-0.18.1
Fetching: railties-4.0.0.gem (100%)
Successfully installed railties-4.0.0
Fetching: hike-1.2.3.gem (100%)
Successfully installed hike-1.2.3
Fetching: tilt-1.4.1.gem (100%)
Successfully installed tilt-1.4.1
Fetching: sprockets-2.10.0.gem (100%)
Successfully installed sprockets-2.10.0
Fetching: sprockets-rails-2.0.0.gem (100%)
Successfully installed sprockets-rails-2.0.0
Fetching: rails-4.0.0.gem (100%)
Successfully installed rails-4.0.0
Parsing documentation for atomic-1.1.13
unable to convert "\xCF" from ASCII-8BIT to UTF-8 for lib/atomic_reference.bundle, skipping
Installing ri documentation for atomic-1.1.13
Parsing documentation for thread_safe-0.1.2
Installing ri documentation for thread_safe-0.1.2
Parsing documentation for activesupport-4.0.0
unable to convert "\x80" from ASCII-8BIT to UTF-8 for lib/active_support/values/unicode_tables.dat, skipping
Installing ri documentation for activesupport-4.0.0
Parsing documentation for builder-3.1.4
/Users/SMD/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/rdoc/parser.rb:87: warning: Unsupported encoding : ignored
/Users/SMD/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/rdoc/parser.rb:87: warning: Unsupported encoding ignored
Installing ri documentation for builder-3.1.4
Parsing documentation for rack-1.5.2
Installing ri documentation for rack-1.5.2
Parsing documentation for rack-test-0.6.2
Installing ri documentation for rack-test-0.6.2
Parsing documentation for erubis-2.7.0
Installing ri documentation for erubis-2.7.0
Parsing documentation for actionpack-4.0.0
Installing ri documentation for actionpack-4.0.0
Parsing documentation for activemodel-4.0.0
Installing ri documentation for activemodel-4.0.0
Parsing documentation for arel-4.0.0
Installing ri documentation for arel-4.0.0
Parsing documentation for activerecord-deprecated_finders-1.0.3
Installing ri documentation for activerecord-deprecated_finders-1.0.3
Parsing documentation for activerecord-4.0.0
Installing ri documentation for activerecord-4.0.0
Parsing documentation for mime-types-1.24
Installing ri documentation for mime-types-1.24
Parsing documentation for polyglot-0.3.3
Installing ri documentation for polyglot-0.3.3
Parsing documentation for treetop-1.4.15
Installing ri documentation for treetop-1.4.15
Parsing documentation for mail-2.5.4
unable to convert "\x80" from ASCII-8BIT to UTF-8 for lib/mail/values/unicode_tables.dat, skipping
Installing ri documentation for mail-2.5.4
Parsing documentation for actionmailer-4.0.0
Installing ri documentation for actionmailer-4.0.0
Parsing documentation for thor-0.18.1
Installing ri documentation for thor-0.18.1
Parsing documentation for railties-4.0.0
Installing ri documentation for railties-4.0.0
Parsing documentation for hike-1.2.3
Installing ri documentation for hike-1.2.3
Parsing documentation for tilt-1.4.1
Installing ri documentation for tilt-1.4.1
Parsing documentation for sprockets-2.10.0
Installing ri documentation for sprockets-2.10.0
Parsing documentation for sprockets-rails-2.0.0
Installing ri documentation for sprockets-rails-2.0.0
Parsing documentation for rails-4.0.0
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/belongs_to.png, skipping
unable to convert "\xF4" from ASCII-8BIT to UTF-8 for guides/assets/images/book_icon.gif, skipping
unable to convert "\x91" from ASCII-8BIT to UTF-8 for guides/assets/images/bullet.gif, skipping
unable to convert "\xF5" from ASCII-8BIT to UTF-8 for guides/assets/images/chapters_icon.gif, skipping
unable to convert "\xF5" from ASCII-8BIT to UTF-8 for guides/assets/images/check_bullet.gif, skipping
unable to convert "\xF4" from ASCII-8BIT to UTF-8 for guides/assets/images/credits_pic_blank.gif, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/csrf.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/edge_badge.png, skipping
unable to convert "\x9E" from ASCII-8BIT to UTF-8 for guides/assets/images/favicon.ico, skipping
unable to convert "\x80" from ASCII-8BIT to UTF-8 for guides/assets/images/feature_tile.gif, skipping
unable to convert "\x80" from ASCII-8BIT to UTF-8 for guides/assets/images/footer_tile.gif, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/fxn.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/getting_started/challenge.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/getting_started/confirm_dialog.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/getting_started/forbidden_attributes_for_new_post.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/getting_started/form_with_errors.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/getting_started/index_action_with_edit_link.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/getting_started/new_post.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/getting_started/post_with_comments.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/getting_started/rails_welcome.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/getting_started/routing_error_no_controller.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/getting_started/routing_error_no_route_matches.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/getting_started/show_action_for_posts.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/getting_started/template_is_missing_posts_new.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/getting_started/undefined_method_post_path.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/getting_started/unknown_action_create_for_posts.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/getting_started/unknown_action_new_for_posts.png, skipping
unable to convert "\xF0" from ASCII-8BIT to UTF-8 for guides/assets/images/grey_bullet.gif, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/habtm.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/has_many.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/has_many_through.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/has_one.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/has_one_through.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/header_backdrop.png, skipping
unable to convert "\x80" from ASCII-8BIT to UTF-8 for guides/assets/images/header_tile.gif, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/i18n/demo_html_safe.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/i18n/demo_localized_pirate.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/i18n/demo_translated_en.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/i18n/demo_translated_pirate.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/i18n/demo_translation_missing.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/i18n/demo_untranslated.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/callouts/1.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/callouts/10.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/callouts/11.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/callouts/12.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/callouts/13.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/callouts/14.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/callouts/15.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/callouts/2.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/callouts/3.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/callouts/4.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/callouts/5.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/callouts/6.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/callouts/7.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/callouts/8.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/callouts/9.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/caution.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/example.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/home.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/important.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/next.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/note.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/prev.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/tip.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/up.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/icons/warning.png, skipping
unable to convert "\xFF" from ASCII-8BIT to UTF-8 for guides/assets/images/jaimeiniesta.jpg, skipping
unable to convert "\xF5" from ASCII-8BIT to UTF-8 for guides/assets/images/nav_arrow.gif, skipping
unable to convert "\xFF" from ASCII-8BIT to UTF-8 for guides/assets/images/oscardelben.jpg, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/polymorphic.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/radar.png, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/rails4_features.png, skipping
unable to convert "\xFF" from ASCII-8BIT to UTF-8 for guides/assets/images/rails_guides_kindle_cover.jpg, skipping
unable to convert "\xEC" from ASCII-8BIT to UTF-8 for guides/assets/images/rails_guides_logo.gif, skipping
unable to convert "\x8C" from ASCII-8BIT to UTF-8 for guides/assets/images/rails_logo_remix.gif, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/session_fixation.png, skipping
unable to convert "\x80" from ASCII-8BIT to UTF-8 for guides/assets/images/tab_grey.gif, skipping
unable to convert "\x80" from ASCII-8BIT to UTF-8 for guides/assets/images/tab_info.gif, skipping
unable to convert "\x80" from ASCII-8BIT to UTF-8 for guides/assets/images/tab_note.gif, skipping
unable to convert "\x80" from ASCII-8BIT to UTF-8 for guides/assets/images/tab_red.gif, skipping
unable to convert "\x80" from ASCII-8BIT to UTF-8 for guides/assets/images/tab_yellow.gif, skipping
unable to convert "\x89" from ASCII-8BIT to UTF-8 for guides/assets/images/tab_yellow.png, skipping
unable to convert "\xFF" from ASCII-8BIT to UTF-8 for guides/assets/images/vijaydev.jpg, skipping
Installing ri documentation for rails-4.0.0
24 gems installed
抱歉无法编辑终端输出。线太多了！