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'
and on the assets
group:
group :assets do
gem 'sass-rails', :git => 'git://github.com/rails/sass-rails.git'
gem 'coffee-rails', :git => 'git://github.com/rails/coffee-rails.git'
# See https://github.com/sstephenson/execjs#readme for more supported runtimes
# gem 'therubyracer'
gem 'uglifier'
end
This set of changes worked for me on Mac OSX 10.8.2
I hope this helps somebody. :-)