Remove gemfiles, Gemfile.lock from version control
Remove gemfiles from Travis
Simplify Appraisals

Test latest Rails 3 version against Ruby 1.9 and latest Rails version
that supports Ruby 2.
Add jquery-rails back to Appraisals
Force Appraisal to build gemfiles for Travis
Restrict gem support to MRI 1.9 and 2.0
Loosen development dependencies
Merge pull request #257 from thoughtbot/dc-remove-gemfiles

Improve testing of different Ruby, Rails versions