Wrote views code for new page: Contest Winners

Contest Winners utilizes the teammates’ ride records to determine
“weekly winners” in the categories of most time spent on the bike, most
miles, speediest rider, and most improved rider. Because I cannot
figure out duration field at this moment, I have delayed implementation
of most time spent on the bike. My next commit will be of a
corresponding page that this code can fill out and an update to the
urls.py file in dashboard.