Welcome post for Algorithms and Blues

Summary:
This is what I think is a perfectly adequate welcome post. I don't plan on
advertising it at all as there's not any technical content, but people may
find it through the internet anyway.

Test Plan: Reading.

Reviewers: endenizen, seans, mgc

Reviewed By: endenizen

CC: ron.buell, ds, amie.kweon

Differential Revision: https://phabricator.rdio.com/D10882