Memory leaks with `Scene.new`

[Watson1978]

1. Scene.new will call scene_alloc
   

   motion-game/src/layer.cpp

   Lines 83 to 94 in df05c12

   	scene_alloc(VALUE rcv, SEL sel)
   	{
   	auto layer = mc_Scene::create();
   	auto scene = cocos2d::Scene::createWithPhysics();
   	scene->addChild(layer);
   	layer->scene = scene;
   	VALUE obj = rb_class_wrap_new((void *)layer, rcv);
   	layer->obj = rb_retain(obj);
   	return obj;
   	}

2. mc_Scene::create(); creates C++ instance

   motion-game/src/layer.cpp

   Line 46 in df05c12

   auto scene = new mc_Scene();

However, there is not delete anywhere.