Some tests failed to override --transit-helper, which meant they
intermittently talked to the real transit server (briefly, before
deciding the local+direct connection was better).
This requires a DB delete/recreate when upgrading. It changes the server
protocol, and app IDs, so clients cannot interoperate with each other
across this change, nor with the server. Flag day for everyone!
Now apps do not share channel IDs, so a lot of usage of app1 will not
cause the wormhole codes for app2 to get longer.
* declare transit records and handshake keys are bytes, not str
* declare transit connection hints to be str
* use six.moves.socketserver, six.moves.input for Verifier query
* argparse "--version" writes to stderr on py2, stdout on py3
* avoid xrange(), use subprocess.Popen(universal_newlines=True)
