cd `bundle show active_record`

gem install qwandry

qw matrix # opens ruby's matrix class in your editor
qw rails  # will ask you which version of rails you want to open
qw activerec 3.1 # will find the gem activerecord 3.1 and open it
You can also use Qwandry with other common languages:
qw -r python numpy # opens python's numpy library
qw -r perl URI # open perl's URI library
qw -r node express # open express if it is installed for node

EDITOR=subl qw activerecord 3.2.14

touch ~/.qwandry/init.rb

register 'projects' do
 add 'your project path'
end

default :ruby, :gem, :projects