Remove commented code.
Do not use wrapper around net.Conn.
Make better use of textproto Reader and Writer.
Formatting.
Handle PING command with PONG response.
Let ReadMessage timeout after 10 seconds.

This is neccessary to detect broken connections. A client has to send PING/PONG
commands in order to test the connection, because the ReadMessage method just
blocks forever if the underlying TCP connection is broken.
Add Close method to client.