Add Retina screens support

Upscale the canvas size when using High DPI screens (http://www.html5rocks.com/en/tutorials/canvas/hidpi/).
Tested on iPhone/iPad.
Add touch events support
jQuery has its custom implementation of event, we need the original one
Merge branch 'patch-1' of https://github.com/fabiocaseri/farbtastic into retina
Merge branch 'retina'
Merge branch 'touch-support' of https://github.com/fabiocaseri/farbtastic into touch-support
Merge branch 'touch-support'
Remove IE support hacks
Merge branch 'remove-msie'