Feature models with Unit Tests

I added a new target with is intended to test building the data models only. `PSModelsTest` is **NOT** intended to be run along with every build of the main target. I'll be adding more test cases as I go along:
    1.  Building an event model from a dictionary
    2.  Retrieving a list from events from a webservice

I also added [OCMock](http://ocmock.org/) to help mocking objects and behaviour (like API calls).

Leave comments a-plenty before merging.
(#11)