Use Facebook's ProGuard fork (2.5x faster for large applications)

Hi,

I’m a developer on Facebook’s Android application. ProGuard was a huge problem for us with build times, so I made a bunch of tweaks which have sped up proguarding Facebook’s Android app 2.5x. It’s a drop in replacement and produces bit-for-bit identical output to stock ProGuard.

https://github.com/facebook/proguard