Embeddable build status

Pull request for adding 'embeddable build status' icon support. See [issuecomment-15067046](https://github.com/mocleiri/github-oauth-plugin/pull/38#issuecomment-15067046) and [the documentation I wrote](https://github.com/4np/github-oauth-plugin_PATCHED/blob/master/README.md#about-the-patch) for more information