oninput instead of onchange for input tags

[please-wait]

The crossfade sample only responds when mouse click is up. This is because you have used 'onchange' in the input tag to trigger the crossfading. Instead, 'oninput' responds real time. As far as I know, the only reason people use onchange is because of IE which doesn't support Web Audio anyway.

I couldn't find the file here to send a PR.