write at the top of rend-spec that reading the design paper

$Id$

[XXX We need to make nicknames in intro* cells padded to 20

 bytes, and maybe have a fixed length for nicknames in the

 descriptor too -RD]

                    Tor Rendezvous Specification

0. Overview and preliminaries

   Read http://tor.eff.org/doc/design-paper/tor-design.html#sec:rendezvous

   before you read this specification. It will make more sense.

   Rendezvous points provide location-hidden services (server

   anonymity) for the onion routing network. With rendezvous points,

   Bob can offer a TCP service (say, a webserver) via the onion

   The members of Ipt may be either (a) nicknames, or (b) identity key

   digests, encoded in hex, and prefixed with a '$'.  Clients must

   accept both forms. Services must only generate the second form.

   Once 0.0.8.1 and 0.0.9pre3-4 are obsoleted, we can drop the first

   form.

   Once 0.0.9.x is obsoleted, we can drop the first form.

   [It's ok for Bob to advertise 0 introduction points. He might want

    to do that if he previously advertised some introduction points,