Added appledoc

Relevant appledoc links:

- [appledoc site](http://gentlebytes.com/appledoc/)
- [Objective-C Documentation NSHipster Article](http://nshipster.com/documentation/) by [@mattt](https://github.com/mattt)
- [Actual appledoc examples and specs](https://github.com/tomaz/appledoc/blob/master/CommentsFormattingStyle.markdown)