1.3 Update

* Added more comments
* Actor setters now only dirty transform if a change is made
* Actor.findActorDeep() removed
* Actor.findActor() has additional parameter that allows recursive
searching
* Actor.sendToBack() added
* Actor.addFixture() now returns the created fixture
* Actor.addJoint() now returns the created joint
* Scenes now active property which can be used to pause processing
* Scenes will now still be processed when not visible
* Scene.findActorDeep() removed
* Scene.findActor() has additional parameter that allows recursive
searching
* Scene.sendToBack() added