Lessen the amount of dependencies

[JK3Y]

I want to implement my own network class using Foundation's built-in NSURLSession since the Alamofire features that are actually used are very little.

Files could be removed and standard FileManager calls can be used instead. It's only a single Swift file for the whole library so it's not adding a lot of bulk to the app.

The Promises framework could also be swapped out for calls to the built-in Grand Central Dispatch. https://github.com/google/promises/blob/master/g3doc/index.md#benchmark shows GCD has speeds 2-4x faster.