don't check in Gemfile.lock, as per discussion at http://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile/
don't check in Gemfile.lock, as per discussion at http://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile/

budnik/schema_associations,dmeranda/schema_associations