Changes when adding strings and images

First off, very cool control. Thanks for putting it out there. 

I made a few changes when adding strings *and* images to a PopoverView and thought others might be interested.

**Changes:** 
* kImageAboveLabel - bool value that positions icons/images above or to the left of labels
* kImageTitlePadding - padding between icons/images and titles in both horizontal and vertical
* UIButtons generated for both horizontal and vertical settings