Use own Common.indexOf method for IE 6-8 compatibility

Conflicts:
	src/core/Common.js
Add Pixi DisplayObjectContainer to allow view bounds in webGL
dont draw offscreen constraints. Set visible flag on offscreen sprites
Merge branch 'master' into topic/addBounds
fixed collision detection issue, closes #12
changed certain Matter.Composite methods to private in docs
added composite events
added composite events example to Demo.events
Merge pull request #31 from mrspeaker/topic/addBounds

added view bounds for RenderPixi
fixed scaling on RenderPixi view bounds
appease jshint
merge tumult:old_ie_fixes + tweaks