#29 Refactor playback

Fix pause() firing before play() finishes (which is illegal)
Allow seeking/pausing before the track even loads
Make rapid skipping more efficient
Fix loop button sometimes not showing
Make next/prev buttons loop
Make prev button seek to start if position is > 10 seconds
Use audio.loop for looping single track
Save playback info in more cases
Possibly some other stuff I felt like changing that may or may not
affect anything