UIButton Subclass with a built-in UIActivityIndicator. Based off the Ladda concept by Hakim El Hattab http://lab.hakim.se/ladda/
JHActivityButton makes use of the AHEasing library.
Known Issues:
- Only kCGColorSpaceModelRGB and kCGColorSpaceModelMonochrome colors are supported for the eased color transform for the background
- Some color transitions may not properly support Back/Elastic/Bounce easing functions. You can't get more black than black or more white than white.