Travis - Add Rails 4.1.0.beta1, get Rubinius running

1. Added Gemfile for Rails 4.1.0.beta1
2. Loosened the minitest dependency for compatibility with Rails 4.1.0.beta1
3. Removed the branches restriction from Travis config so Travis would run on PR branch
4. Fix Rubinius label and added missing Rubinius gems to gemfiles to get the Rubinius builds running again.

The Rubinius build is now failing instead of erroring - there's an error message mismatch between the expected (based on MRI) and the message generated by Rubinius.  Otherwise Rubinius works as expected.