Replace RAC with completion blocks for networking
Update unit tests to remove RAC.
Remove RAC from the project

* Remove the submodule
* Remove view/view controller use of RAC, moving TaskCellViewModel
binding logic into TaskCell
Update README to remove RAC notes
Remove forward declaration of RAC class
Merge pull request #225 from brendonjustin/feature/removeRac

Remove ReactiveCocoa and reimplement affected functionality