South doesn't properly deal with removing the Django User model, so
this commit redoes our South history to instead start after that
migration has already been applied. This allows us to get rid of some
annoying hacks.
Note that developers and staging will need to run
./manage.py migrate --delete-ghost-migrations zephyr
in order to clear out the old versions of the migrations.
(imported from commit 7f45ea601b809dde33720f76e7dfb0ab348b0e65)
Tim Abbott