iOS 8 Support

Added new iOS 8 threading/queue methods to remove deprecated message.
High Quality Scaling

Set interpolation quality to high in the
imageCroppedAndScaledToSize:contentMode:padToFit: method.
High Quality Drawing

Set interpolation quality to high in all relevant methods to eliminate
jagged edges on drawing.
Macros

Added macros to fix compiler issues for older code with older versions
of Xcode
Macros

Compiles without errors in both Xcode 6 and Xcode 5
Merge pull request #17 from thefirstnikhil/master

iOS 8 Support + High Quality Scaling/Drawing