join's how devices will create or join existing games. It more
compilicated than I'd like but seems to work except that once a slot's
assigned it's unavailable to anybody else even if the other fails ever
to respond (i.e. needs the ACK function of the c++ relay.)
ACK doesn't need to wait 2 seconds for a reply, and when it does so the
next send waits too. Eventually we'll want to combine messages already
in the queue into a single send. For now, this makes things better.
So far uses curl and json-c to send b64-encoded data to new script
which is able to echo the data. Next that script will need to open a
UDP socket to the relay and return results that appear before timeout.
