Weekly headlines command

Review Request #2959 — Created March 15, 2012 and discarded — Latest diff uploaded

Review Board
Original idea from google code wiki:
Finding out what's been happening on Review Board isn't always easy. It might be worthwhile to have users be able to opt-in to weekly email updates from Review Board that tell them useful things about the groups that they belong to. In particular, it could mention things about:
- Outstanding reviews that they could / should tackle
- A list of review requests that have been marked submitted, and which ones have been discarded
- A list of new review requests
- Perhaps something like, "the top reviewer of the week"
- Perhaps more... 
Successfully printed "Hello from Weekly Headlines" when typing "./reviewboard/manage.py weekly-headlines".