Improve/reintroduce subtitles

Refactored the code from the custom popover into a new class called HYPSubtitleView. It uses the section position to determine which way the arrow should point. This refactoring also solves the view hierarchy problem that we had with the popover view controller solution.

![screen shot 2014-12-20 at 13 26 37](https://cloud.githubusercontent.com/assets/57446/5514795/da954702-884b-11e4-9a79-32d0ac41dc0c.png)
![screen shot 2014-12-20 at 13 26 40](https://cloud.githubusercontent.com/assets/57446/5514796/da9d9f42-884b-11e4-9b4e-7c8fe27a28cd.png)
![screen shot 2014-12-20 at 13 27 35](https://cloud.githubusercontent.com/assets/57446/5514799/f95bbe50-884b-11e4-8613-3e35b044f369.png)