Fix Travis tests

 - [x] Fix some tests
 - [x] Adds a secure `GITHUB_API_TOKEN` env variable for travis which will get around the API limits that usually cause builds to fail
 - [x] Test against Ruby `v2.0.0` for Mavericks

Alas this doesn't work for forks / pull requests unfortunately. I'm happy to put in a public read only token from a dummy account (@boxen-tester), but its obviously not good practice, thoughts? /cc @createdbypete