Fixed bug where spying on a method that releases an argument causes a crash on -[NSInvocation retainArguments]. Fixes #137.

Moved spec to its own describe block.
Add 7.0 SDK build to .travis.yml
Added tests for spying on objects those using KVO
Fixes known basic edge cases when spying on Key Value Observers and/or observed objects

- TODO: should be expanded to cover collection observing.
- Caveat: when under KVO, spies will not record messages sent to themselves.

Special thanks to Pavel Taykalo for raising this issue and providing some 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)