Todo
Implement commit statuses (but not combined status)

Combined status doesn't work on GitHub Enterprise: "If you would
like to help us test the Combined Status API during its preview
period, you must specify a custom media type in the 'Accept' header.
Please see the docs for full details." but there is not such thing
in the doc https://developer.github.com/v3/repos/statuses

Conflicts:

	PyGithub/Blocking/tests/Framework.py