Fixed iOS 8 middle arrow popover.
Fix for corner cases.
We want the size of the image to matches the pixel-based dimensions of the image.   Source: UIImage Class Reference
Moved images to correct directory and added a read me.
Tweak wording of popover image readme.
Merge pull request #187 from MIT-Mobile/3.6/ipad-mit-popover

Fix for MIT Popover not displaying correctly on iOS 8. Fixed #185