Update Travis to use Appraisal gems

1. Updated the Appraisal dependency in the gemspec
2. Removed Appraisal from the base Gemfile
3. Updated the Appraisal file to use current (non-beta) versions
4. Rebuilt Appraisal gemfiles
5. Removed unneeded Appraisal gemfile locks so Travis can rebuild as needed
6. Updated .travis.yml to use Appraisal gemfiles, excluding Ruby 1.9.3 for ActionPack 4.0/4.1

Specs run green on Travis