说明：  四种亮灯方式自由切换的跑马灯程序，若想在最开始就体会到学习verilog的乐趣，那就先学习跑马灯程序吧
(Marquee program four free switching of lighting the way, if you want to appreciate at the very beginning of learning verilog fun it would be to learn Marquee program)