Add mini-symposia selection criteria.
Add mailings directory and process-template.py.

For email templates.
Add mini-symposium chair request template.
Rename chair_request -> chair_invitation.
Add review board invitation mailing.
Draft Call for Submissions.
Draft initial conference announcement.
Draft the call for conference abstracts.
some announcement edits.
Merge pull request #1 from scopatz/mm-mailings

some announcement edits.
Merge pull request #1 from thewtex/mailings

Adding all the great content put together by Matt and Katy for announcements.