* Implement Issue Timeline preview API
* Add DebuggerDisplay to response models
* Rename method
* Add Observable Issue Timeline client
* Add that missing property thing
* Add teh comments
* Added unit tests
* Fix method names
* Add missing event type enum and API preview accept header
* Add integration tests for async client
* Pass in API preview header
* Add observable integration tests
* Unbreak the broken tests...
* Remove unnecessary usings
* Add missing events
* Fix API URLs
* Add overloads for using repository Id instead of owner/repo and paging
* Add tests for repository id overloads
* Add paging tests
* I'm clearly a bit rusty about this test thing here...
* Missed a check for null argument
* Added missing XMLDocs
