Make Flixel GPU accelerated

I am really happy to issue this pull request. It makes Flixel Community GPU accelerated by using [Genome2D](genome2d.com) as a render.

This is the first step to bring Flixel to the GPU world, there is still room for improvement. Despite of that I've ran [some tests](http://www.as3gamegears.com/blog/making-flixel-community-gpu-accelerated/) and the new GPU render is way faster than the CPU blitting one.

I have tried to keep changes to a minimum, avoiding modifications that would break too many things. I think the only significant modification I've made that deeply changes the current API was the addition of a `Camera` param in `FlxBasic#draw()`, which is now `FlxBasic#draw(Camera:FlxCamera)`. There was no way I could think of to implement multiple cameras without that change.

Special thanks to @pshtif and @Beeblerox for helping making it happen!

Fix #90