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
added Body.setMass, Body.setDensity, Body.setInertia
removed engine.input, removed Engine mouse events, added MouseConstraint mouse events
changed Mouse.create to return as a plain object
removed redundant property
changed Grid.create to accept an options object
removed engine.broadphase.current, removed engine.broadphase.instance, changed engine.broadphase to refer to the broadphase instance, updated matter-tools
added docs for engine.timing.isFixed
added time scaling to Sleeping
changed Sleeping constants to be public (module level)
appease jshint
fixed Body.rotate
moved collision events into Engine.update, changed collisionStart to trigger before collisions resolved
fixed incorrect bounds issue when passing angle in Body.create
fixed collision detection issue, closes #12
changed certain Matter.Composite methods to private in docs
added composite events