Integrate with Twitter's API

This would allow the following:

Tweet on a user's behalf every time they update their public key. Users should rotate their keys on a fairly regular basis since Perfect Forward Secrecy is not a feature of PGP. Maybe consider integrating with other services like pushover.net so users can be notified immediately on their mobile device when a key changes.

Integrating more closely with Twitter has the added benefit of advertising keybase to a massive audience. Every key change (or new proof) is an advertisement for the service to all followers.

In addition, it would be great to see a list of people I follow on Twitter who also have keybase profiles. And be notified (via Twitter DM, @reply, email, etc.) when someone I follow creates a keybase profile.

Also, consider integrating with FaceBook for key updates. This type of integration is something your average crypto nerd won't want but I think the long term goal is to turn keybase into something that brings "crypto to the masses" right?

The issue names no files, tests, or entry points. First narrow the scope among Twitter posting, follow matching, direct notifications, Pushover, and Facebook, then define an acceptance criterion for the selected integration before implementation begins.

Written by the indexing model from the issue text.