Devices might not get detected

[JaniM]

Originally reported in likethemammal/daisywheeljs#25

Here's some info:

• Platform: Windows
• Browsers tested: Google Chrome 63.0.3239.84 (64b) and Firefox 57.0 (64b)
• Controllers tested: Generic Xbox 360 controller and Hori RAP 4 (DS4-emulative)
• http://html5gamepad.com/ recognizes the controllers properly, even when both of them are plugged in
• http://likethemammal.github.io/gamepad-micro/example.html recognizes neither, even one by one
• Steam is likely to be interfering with the controllers, but I didn't find any difference with it being off