When someone starts DJing, their playlist "cycles", i.e. the first item is moved to the very end. A socket event (playlistCycle, perhaps) should be dispatched for this too, so clients also know to cycle their playlist.

Advance stuff happens here, for now:
https://github.com/goto-bus-stop/u-wave-api-v1/blob/8ad01591dfe77948312bbdbad3a72ba3066667d7/src/sockets.js#L222-L244