Major changes:
* Changed the structure of the scripts, as reflected in the readme for easier mainainability
* Compilation works for armv7, armv7s and x86_64. Tested against XCode 5.1, Mac OS X 10.9.2, iOS 7.1
* Updated IM_Test project (more to be done there...)
* Bumped jpeg to 9a and png to 1.6.10