Add self to people; 1st draft of mirage-tcpip post.

Comments and suggestions are very welcome.
`a useful high-level functions` <- remove a
also, I'd explain it briefly: while listen_udpv4 and listen_tcpv4 register a callback for a given port, listen enters the receive-loop and demultiplexes packets to the registered callbacks. (what about multiple listeners for a single port?)