supproted Window.caption, Window.caption=, but not implemented spec.
changed Image drawing methods return self.
supported Input.pad_push?.
supported Window.width, Window.width=, Window.height, Window.height=, Window.open_filename, but not implemented spec.
added Input.set_repeat spec.
added DXRubySDL::Window.caption, DXRubySDL::Window.caption= spec.
fixed style.
fixed Input.key_push?.
fixed style.
refactored Input.sdl_key_press?.
refactored using Input.sdl_key_push?.
refactored Input.