Deprecating tor-talk mailing list

As we now have a Tor Forum, with distinct categories about Tor (General Discussions, User Support, UX, Feedback, Blog comments), I believe it's time to archive the tor-talk mailing list.

A short plan:

• Define a date to archive the tor-talk mailing list.
• Create a topic on Tor Forum announcing tor-talk retirement.
• Send an email to tor-talk and invite contributors to join the forum.
• Bounce tor-talk emails and refer to the Tor Forum topic.