OSX Support

Resolves #5.

In this branch, all mentions of `UIView` in the code are replaced with `ALView`. The latter, depending on the platform, is typealiased to either `UIView` or `NSView`. The APIs are so similar that no other changes to the code were really necessary.

The new OSX targets just use the same Swift files as this iOS versions do, so the only things that had to be added were the Info.plists and the OSX app delegate / main.swft files.

Enjoy :)