我正在尝试使用collectiveidea的delayed_job gem 安装说明包括
Rake tasks are not automatically loaded from gems, so you’ll need to add
the following to your Rakefile:
begin
require 'delayed/tasks'
rescue LoadError
STDERR.puts "Run `rake gems:install` to install delayed_job"
end
我的 Rakefile 在哪里?什么是 Rakefile?