Adding UFPopover assets and general bug fixes

- Added default error and success popover icon.
- Added support for iOS 6.
- Fixed bug with sizing for UILabel with iOS 7.
- Fixed bug with attribtuedTextDelegate on UILabel.
- Added version checking block to UIDevice.
- Added documentation to final NSAttributedString+UFKit methods.
- Added setTextAlignment to NSAttributedString+UFKit.

Signed-off-by: Michael O'Brien <michaelobrien.resides@gmail.com>