Add a ToAsyncEnumerable overload for tasks. I always felt it was missing as there is a ToObservable overload for tasks too.
Added unit tests for new ToAsyncEnumerable overloads.
Removed #if HAS_AWAIT since I did not use await after all.
Merge pull request #11 from Blewzman/AddToAsyncEnumerableOverloadForTasks

Add ToAsyncEnumerable overload for tasks.