only flush datachannel with nonzero bytes, which prevents Tor from marking the SOCKS for close (#12)

remove webRTCConn SendLoop and simplify Write without additional channel, as net.Conn is already safe

clean up ice candidate log message.
still need to debug the copy loop break.

log traffic bytes only once every few seconds, along with OnMessage & datachannel.Send counts, to prevent flooded logs

request handlers

Seems unlikely to work due to dev_appserver single inflight request limitation