Merge branch 'django-1.6' into re
Makes recurring events work

Recurring events all have the same UID. Instead of assuming it is
unique, this checks the last modified date *and* UID to determine if
existing shifts need to be replaced.

(cherry picked from commit 09ad8783e9ec2aee10f44c26be36da9d5faa7ab3)
Merge branch 'django-1.6' into recurring-events
Re-number migrations
Merge branch 'django-1.6' into features/irc
Re-number migration
Merge branch 'features/irc' into deploy
Merge branch 'recurring-events' into deploy