Added plugin to log private and public Github commits.

I created a new plugin(which is really just a modified version of githublogger.rb) to log Private and Public Github commits. I've added a configuration parameter for an OAuth token, along with link to instructions for generating one from the command line.

I named the plugin githubcommitlogger.rb. I'm not sure if that's really an ideal name, let me know if you'd like me to change that.