Print message when new client connection is made to python server.
python: Catch KeyboardInterrupt exceptions.

Avoids a stack trace output when user hits Ctrl-C.
python: Set default for option list to empty list.

Avoids an exception when no subscribe options are given.
python: Add send() method to Commander class.

Catches socket errors to avoid an uncaught exceptions.
python: Refactor client to allow line editing.

Added SocketReader class to move reading input from socket into a child
thread. This allows the Commander class to use the cmdloop() method to
read directly from stdin thus enabling command line editing via
readline.