Feature: Add websocket to determine the beginning of the next round

[vlow]

Add a websocket to the server which sends out a small ping whenever a new round begins (e.g. containing the round number). Check this delicious piece of software: https://github.com/joewalnes/websocketd

[Moritz H.]

Done. Check this: https://github.com/phxql/restwars/blob/master/docs/webservice.md

[vlow]

Wow, nicely done! This renders a lot of bloaty synchronizing code in the clients redundant!