Add support of organization events

[n0str]

Would be nice to have repository added message.
However, now even ping event does not work.

debug()          Ping event payload taken {'zen': 'Design for failure.', 'hook_id': 291349016, 'hook': {'type': 'Organizati
debug()          Cannot process PingEvent payload because of 'repository'
debug()          Cannot handle request from GitHub: 'NoneType' object has no attribute 'full_name'