new bindings for Pixi.js
isinstance can now be called from inside "with javascript:" blocks.
moved isinstance, issubclass, getattr, setattr, and type to runtime/builtins.py
Pixi.js hello world
Pixi.js bindings: added mouse/touch callbacks
fixed: for loop over string and JSArray, fixed if 'x' in 'xyz', removed __CONTAINS__ hack from get_attribute.
fully removed __CONTAINS__ hack.
added getter and setter to __class__.__properties__