RigidBody::parent now is simply a raw pointer instead of a shared_ptr
RigidBody::parent now is simply a raw pointer instead of a shared_ptr

sheim/drake,billhoffman/drake,sheim/drake,billhoffman/drake,sheim/drake,billhoffman/drake,sheim/drake,sheim/drake,billhoffman/drake,billhoffman/drake,sheim/drake,sheim/drake,billhoffman/drake,billhoffman/drake,billhoffman/drake,sheim/drake