Joystick Visualizer

I figured it would be nice for us to have a simple tool to test the joysticks as we develop them, so I made a python script that does so. I've committed the script to the script to the USB Gamepad repository so anyone working on a joystick can use it. I've tested it with an off-the-shelf joystick, so it should have the same button mapping as a standard joystick. Here's a screenshot: