Switch from Pollymer to Socket.IO/TornadIO2
Remove unused crap & get Socket.IO connecting, yay
Use same host/port as HTTP instead of hardcoding

So, I don't understand why the separate `socket_io_port`
setting exists. It seems to work fine connecting over the
regular port, and the original, Node.js-based implementation
of Socket.IO doesn't mention using a second port.