Add URL for the Contest Winners page to dashboard/urls.py
Bug fixes to new contest_winners function in dashboard/views.py
Beginnings of Contest Winners page.

Heavily stolen from index, because I have next to no understanding of
CSS. I would like to eventually have it show the riders’ names and
pictures, and the winning stat associated with them. Right now I don’t
have time to fully complete it. That should happen later this week.