change method signatures of Lita::Handlers::GitHub

For some reason I prefixed the methods in this handlers with `gh_`. This removes that weird convention:

`gh_status()` => `status()`
`gh_version()` => `version()`
Merge pull request #13 from PagerDuty/change_method_signatures

Merge pull request #13 from PagerDuty/change_method_signatures

change method signatures of Lita::Handlers::GitHub