Appraisals

This uses the [Appraisal](https://github.com/thoughtbot/appraisal) project to test vagrant-rackspace against multiple versions of Vagrant.  Travis will automatically test each version.  Locally, you can test each version by running `appraisal install` and then `appraisal rake`.

This will let the project take advantage of new Vagrant 1.4+ features, while still making sure there is still a fallback or backwards compatible implementation for Vagrant 1.3.x.

I also added Ruby 2.1.0 to the list of Rubies to test.