我似乎无法解决这种依赖关系。我已经尝试在 Gemfile 中明确设置版本，但似乎没有任何效果。有什么想法吗？
Gem::LoadError: Unable to activate activemodel-3.2.8, because builder-3.1.3 conflicts with builder (~> 3.0.0)
~/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/site_ruby/1.9.1/rubygems/specification.rb:1637:in `raise_if_conflicts'
~/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/site_ruby/1.9.1/rubygems/specification.rb:746:in `activate'
~/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:51:in `block in require'
~/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:50:in `each'
~/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:50:in `require'
这是我的Gemfile：
# encoding: UTF-8
source :rubygems
source :gemcutter
source :rubyforge
gem 'sinatra'
gem 'mongoid', '~> 2.4'
gem 'mongo', '1.6.2'
gem 'bson_ext', '~> 1.5'
gem 'builder', '~> 3.0.0'
gem "mongoid-history"
gem "mongoid-rating"
gem "mongoid_vote"
gem "geocoder"
gem "slim"
gem "sidekiq"
gem "sprockets" #required by sidekiq for some reason...
gem "logger"
gem "carrierwave"
gem 'carrierwave-mongoid', :require => 'carrierwave/mongoid'
gem "mongoid-history"
gem "airbrake"