Migrate to Swift 2.3 and Swift 3

In order to migrate and test our app to Swift 2.3/3.0 prior to the release of Xcode 8 and iOS 10, all of our dependencies need to be migrated first.

This can be solved by pointing our podfile to those respective Swift 2.3/3.0 branches, but this repo does not appear to have either of those branches.

This blog post contains helpful tips for migrating open source libraries.