You will have to make some changes to your Gemfile to get it working.
Basically what I've changed was:
gem 'rails', :git => 'git://github.com/rails/rails.git'
gem 'activerecord-deprecated_finders', git: 'git://github.com/rails/activerecord-deprecated_finders.git'
gem 'journey', :git => 'git://github.com/rails/journey.git'