Activation emails were using django's sites framework which always has
the domain set to zulip.com.
(imported from commit b81eae96e1a75b64dd93970760b869f3271ce88c)
django.utils.timezone.now returns an aware datetime object because USE_TZ =
True.
Fixes#80.
(imported from commit c60f491fe00a98626ecced94fc3ea1f71f939a38)
I am pretty sure there's no point to using a hash at all. But until I hear
back from the author, let's at least make sure we put as much entropy into the
hash as we expect to get out of it.
(imported from commit 51a231adeab014cc1af8cb67e89baf06e0a1f593)