Renderers

Moved code for rendering team details and team history into a separate team_renderer.py. Three handlers, TeamCanonical, TeamDetail, and TeamHistory invoke these renderers.

The behavior is as follows
(canonical) /team/XXX -> renders current year if participating this year, otherwise renders history page
(detail) /team/XXX/YYYY -> renders given year or 404's if didn't participate in that year
(history) /team/history -> renders history page

Not sure if this is the cleanest way to do this. Suggestions welcome.