Forces one to be an admin to delete
Merge branch 'master' into groups
More stuff with regard to group privacy!
Adds the start of public groups
Merge branch 'master' into groups
Backend of public groups
Merge branch 'master' into groups
Fixes typo
Merge branch 'master' into groups
Merge branch 'master' into groups
Only allows admins to remove other users from a group
Merge branch 'master' into groups
Adds initial caching infrastructure.
Adds field for users to choose when they want their reminder email to be
sent out.
Further improves leaderboard performance.

In particular, makes the leaderboard only depend on whether the user is
anonymous, rather than on the user's specific friends and groups.  In
practice this is a small change since most users have at least
PRIVACY_NORMAL for logged-in users.  Also some more random unrelated
performance tweaks.
Moves leaderboard tags to a separate page.
Start of email reminders; to be continued after more sleep happens.
Moves mobile regexes into utils
Properly links to group graphs.
Merge branch 'master' into caching