Cocos2dv31

Updated repo to use cocos2d 3.1; now using submodules. Not sure how to update license to reference multiple authors, or how much that matters... 

Help/code pieced together from https://github.com/NoodlFroot/smooth-drawing and http://forum.cocos2d-swift.org/t/2-x-to-3-1-shader-help/14015

On my fork I made separate branches for cocos2dv31 and cocos2dv2 ... not sure the best way to do a pull request, either. Hope this all makes sense. :)