Replaced UIButtons in Stats with UISegmentedControl

Fixes #1399 

Replaced the UIButtons that were simulating the functionality of a UISegmentedControl in the native stats screen.  Buttons were not changing color on touch down inside which gave zero hints to the user that they were tappable or that there were different choices.  I suspect accessibility was also interesting as it may not have been obvious the two to three buttons next to each other changed the same thing.

UISegmentedControl has similar styling the buttons with the exception of the grey background color.  I felt that the background color wasn't in the spirit of iOS 7 so I left it the standard white.  There is another issue here to address the overuse of the blue color as this is the "active" or "tappable" color in the app.

![stats before after](https://cloud.githubusercontent.com/assets/373903/2655448/49109e18-bfe6-11e3-8cd8-dca2bc506af7.png)

I'm not entirely happy with the structure of the native stats screens (object inheritance is a bit odd in some cases) but that will be addressed later.