Spies now record messages they send to themselves

- This approach relies on a private NSInvocation method -invokeUsingIMP:
- This should be okay since folks shouldn't be submitting test suites
  for AppStore approval
- Fixes [#34445931]
Merge pull request #96 from pivotal/record-spy-invocations-on-same-spy

Spies now record messages they send to themselves