Pull Request - Fix up

Hey @tLewisII ... Great work on the MDMFetchedResultsCollectionDataSource 

Noticed you had an outstanding Pull Request (https://github.com/mmorey/MDMCoreData/pull/7) with @mmorey. 
It was just sitting there and I thought I'd fix up his feedback/comments 
(_also, it would be really handy for me as I'd like to use it in a project I'm working on_)

__Work done:__
Added CollectionView example using `MDMFetchedResultsCollectionDataSource`
Addressed @mmorey feedback

I left you work on `MDMFetchedResultsCollectionDataSource` largely untouched, with the exception of
initialising: 
* `sectionChanges`
* `objectChanges`  

The majority of my work was addressing feedback and creating the example implementation.
  

Please feel free to review and hopefully pull into your `master` ... which should auto-magically update your outstanding pull request with @mmorey
Let me know if it doesn't .. and I'll try to raise a PR with his repo directly.