updated to remoteStorage.js 0.7.0 and switched to using /public/music

hi! this is the version i published on https://unhosted.org/apps/ - you may not like it because it needs the music to be in /public/music, but in case you do, here is the pull request.

i noticed that the player skips back 2 songs instead of 1 if you click the 'previous' button, will have a look to see if i can fix that still.