bugsnag/bugsnag-ruby — pull request #72 by ConradIrwin (2013-12-27 00:21:29+00:00)
Title: Use bundler as recommended for gems

This means that you can run 'bundle exec' in this directory to use the current
development version of the gem.

http://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile/