Convert to Swift 2.2

[samuelbeek]

First of all, thanks for writing this nice example project and the article that it came with, it has been really helpful.

I converted the syntax to Swift 2.2 so it will compile on Xcode 7.3 without any warnings or errors.

There are some force unwrapped optionals, they were in it before converting the project too, which I'd rather not have in there, but they're pretty harmless.

Let me know if you have any questions. Hope you merge this in, because everyone has to do this by hand now.