Add back button and track info output

- Back button to return to sounds list when in playback/vis mode.
- Track info now displayed over the top of the vis area.
Implement image preloading

- Preload images from imgur after user authenticates
- Limit images loaded to 10 (easier on bandwith)
Implement primitive kick detection

draw method now uses volume changes to detect when to switch out the
current meme image for another.
Fix up commenting and turn uglify back on