Loosen minitest dependency.  Add Gemfile for Rails 4.1.0.beta1

Remove the branches restriction from Travis config.

Get Rubinius running again

Add Rubinius gems
Add rubinius-developer_tools so Coveralls doesn't error.  Explicitly add 'json' gem to Rails 4.0.x case, as it isn't explicity required (but is used) by Rails 4.0.x
Merge pull request #729 from petergoldstein/feature/rails_4_1

Travis - Add Rails 4.1.0.beta1, get Rubinius running