BEARS COVERED IN PIXI DUST!!!

I've been playing around with pixi, and it seems pretty low level, but it does help out a bit. The previous version was breaking, but it looks like things are fixed now. They even have a fancy pants dev version that we can start using that makes it way easier to debug. 

I've downgraded browserify because I couldn't quickly get the new version working, and it wasn't very fun to debug it. 

Sorry for the huge commit, but I added everything in node_modules. I figured we should either add everything in node_modules or add it to the .gitignore. I don't care either way. 

I added the bear walk sprite as an example. We can now easily hook up touch events to sprites. I played around with animating the bear, and it was fun, but I left it out as it wasn't very practical yet.

Next step will be to add a background sprite and hook up touch events to it and get the bear moving.