Update Gosu HelloWorld class
Update Gosu HelloWorld class

yukihirai0505/tutorial-program,yukihirai0505/tutorial-program,yukihirai0505/tutorial-program,yukihirai0505/tutorial-program,yukihirai0505/tutorial-program,yukihirai0505/tutorial-program,yukihirai0505/tutorial-program,yukihirai0505/tutorial-program,yukihirai0505/tutorial-program