Skeleton Refactoring

There are a couple of components to this PR:

* Resolves #1 
* Refactors some more of @juleswhite's initial architecture
* Adds `AFNetworking` for all of the networking plumbing, including a lot of stubbed out methods that @marissamarym can use for this sprint
* Adds initializers and factory methods to all of the Model classes, in iOS style

Everyone please look over this, and once everyone signs off, we can merge.