Make ObservableStarredClient accessible through ObservableActivitiesClient
Merge pull request #351 from nigel-sampson/observable-starred

Make ObservableStarredClient accessible
Merge branch 'master' into watched-client

Conflicts:
	Octokit.Reactive/Clients/IObservableActivitiesClient.cs
	Octokit.Reactive/Clients/ObservableActivitiesClient.cs