Add missing attributes to event type #275

Current GitHub.Data.Event data structure ( https://developer.github.com/v3/activity/events/ ) is partially implemented.

I would need some more data for these Events:

• Event Organisation (if any)
• Event Repository
• Event Type ( https://developer.github.com/v3/activity/events/types/ )

Parsing payload seems too tricky to implement for now…

I already implemented this feature request, but it depends on some integration tests added in PR #274 . I'll wait for PR #274 to be merged before submitting this change in order to minimize conflicts.