Ensure that weekly reports show work done on Sundays.

Because the code used datetime objects rather than date objects, the week_end
parameter would be midnight Sunday, so any statuses created during Sunday
would be considered not part of the week.

I didn't manage to get the code running (gps would suggest [virtualenvs](http://gregoryszorc.com/blog/2014/07/15/python-packaging-do%27s-and-don%27ts/)), so this fix is likely busted.