Buildbox Service Integration

Created by: keithpitt

Hi, I've added integration with my CI product https://buildbox.io. I've matched my service with the GitLab CI service. I've shipped GitLab support to Buildbox today, which includes the endpoints necessary for the merge request status and badges. I needed access to merge requests events so I refactored the service hooks to include the events and included them in merge request changes. I hope that's OK.

Please let me know if theres anything I need to do to get this merged into master.

Thanks! Here are some images of how it all looks: