Currently to tweak the bundler Gemfile, it makes it difficult to track the master repo, and everytime it is updated changes have to be merged. Seperating out customizations into a separate file would largely address this.

See the following for details on how to do this: http://stackoverflow.com/questions/4244182/how-to-customize-gemfile-per-developer

We need to add Gemfile.local.rb to .gitignore as well.