Paint oscillascope with pixels

Fix for #69. I'd love @paez to take a look before I merge. This will obviously look incorrect until we solve #71.

![screen shot 2014-11-21 at 4 35 54 am](https://cloud.githubusercontent.com/assets/162735/5137503/f32d89a0-713a-11e4-8602-0383cf695250.png)

Live preview: https://cdn.rawgit.com/captbaritone/winamp2-js/pixel-oscillascope/index.html