Fixes some basic edge cases with spies and KVO

- Spies can record KVO-related messages sent to and from observed objects.
- TODO: should be expanded to cover collection observing.
- Caveat: while under KVO, spies may not record messages sent to themselves.

Special thanks to Pavel Taykalo for raising some of these issues and providing useful failing specs.
Refactor to avoid breaking test around methods which aren’t forwarded by public runtime mechanism
Clean up project organization a bit

- Moves spec helper objects into support group (not like it sounds)