Travis Update

1. Updated Travis config and Appraisals to reflect the Rails 4.x requirement
2. Removed now obsolete gemfiles
3. Added a Rails 4.1 gemfile
4. Removed 1.8.7 and 1.9.2 from Travis (not compatible with Rails 4.x)
5. Added 2.1.0, jruby-19mode, and rbx to Travis
6. Updated test_helper to use minitest

Everything runs green after these changes.