Added Closure Compiler compatibility + advanced opt. + min.

Great fundamental and dead simple tool!

I am currently feeling performance-crazy and modified it a bit to make it compatible with closure compiler (compilation failed with default settings because of properties like ".package") and finally were able to push it through advanced optimizations with zero warnings. All tests pass. Compile script for ccjs as well as minimal environment and pkginfo externs are included. Pull if you wish.

Cheers