Emitter.setScale now allows you to scale the x and y axis of the particles independently.
Fixed World.restitution typo.
Updated World to use the new p2 defaultContactMaterial.
P2.World has a new contactMaterial property, which can be configured like a normal P2 Contact Material and is applied when two bodies hit that don't have defined materials.
p2.World.defaultRestitution has been deprecated and is now p2.World.restitution.
p2.World.defaultFriction has been deprecated and is now p2.World.friction.
p2.World now uses 4 bodies for the world boundaries, rather than 1 body with 4 shapes. This helps the broadphase massively.
p2.World bounds are now included in the callback events such as beginContact and impact events.
Removed un-used vars.