Defines and implements the CoreTextArcView custom UIView subclass to draw text on a curve.
Based on CoreTextArcView provided by Apple for Mac OS X at https://developer.apple.com/library/mac/#samplecode/CoreTextArcCocoa/Introduction/Intro.html
Ported to iOS (& added color, arcsize features) August 2011 by Alec Vance Juggleware LLC http://juggleware.com/
For discussion, see Stack Overflow entry here: http://stackoverflow.com/questions/3841642/curve-text-on-existing-circle/7114184#7114184