Add submodule ocmock.

Reference
https://github.com/erikdoe/ocmock
http://nickhart.com/ocmock-update/
Change submodule ocmock from ericdoe to fork github.com/beepscore/ocmock.git

This way I can make changes local to the fork.
Open Xcode, drag ocmock from Finder into project navigator. Don't add ocmock to any targets.
In Xcode target BSOperationPlayTests Build Phases / Link Binary With Libraries add libOCMock.a
Update submodule ocmock.
In BSOperation.xcproject delete group ocmock. In BSOperation.xcworkspace add project.

Adjust header search paths and other linker flags.
In BSOperationControllerTests import OCMock.h and uncomment testDesignatedInitializerSetsNotificationCenter.

All 7 unit tests pass.
Merge branch 'ocmock'
Use $ git merge --no-ff to show branch in history.