initial Lita::Handlers::Github commit

This is 0.0.1 of the `lita-github` gem. It adds the Lita::Handlers::Github handler which has two commands:

* !gh status (get the system status)
* !gh version (get the version number of the handler)

It also adds the usual Rubygem scaffolding.
Merge pull request #1 from PagerDuty/first_development_effort

initial Lita::Handlers::Github commit