Fix default Pod names for new users.

Empty default Pod names were causing some confusion on the Checklist
index screen.  These Pods were being created when the auth.User was
first created.  The issue was that users that log in via Facebook get an
auth.User created for them with no username at first - for these users,
we won't create their UserProfile and default Pod yet.  Instead, we'll
let the signal handler for creating a FacebookUser model handle that,
since at that point we know we have a fully flushed out auth.User model.
Add Export link for Checklists to export to CSV.
Rebuild production CSS.