Add Appraisals to Ruby filenames

Thoughtbot's [appraisal](https://github.com/thoughtbot/appraisal) gem is nearing a 1.0.0 release! This super-helpful library allows you to test your Ruby library against different versions of gems by using separate Gemfiles. Appraisal files, like Gemfiles, are run by Ruby.

Here are a few examples of Appraisals being used on github:
* [thinking-sphinx](https://github.com/pat/thinking-sphinx/blob/master/Appraisals)
* [paperclip](https://github.com/thoughtbot/paperclip/blob/master/Appraisals)
* [factory_girl](https://github.com/thoughtbot/factory_girl/blob/master/Appraisals)
* [shoulda-matchers](https://github.com/thoughtbot/shoulda-matchers/blob/master/Appraisals)
* [secretary-rails](https://github.com/SCPR/secretary-rails/blob/master/Appraisals)