Challenges can now be joined up to a quarter into the challenge.
added django-debug-toolbar and used it to slay tons of N+1 Selects.

A few metrics:

challenges page -- 30 queries, 13 Queries
45ms, 53ms

Walk it Off -- 24 Queries, 12 Queries
31ms, 24ms

Just Ride -- 24 Queries, 14 Queries
35ms, 26ms

Warm Up -- 18 Queries, 12 Queries
49ms, 41ms

My Profile -- 30 Queries, 10 Queries
44ms, 71ms????

Team Up! -- 111 Queries, 23 Queries
261ms, 74ms

Account -- 9 Queries, 9 Queries
12ms

Mate Page -- 66 Queries!, 10 queries
88ms, 41ms
Merge branch 'refs/heads/master' into strava-integration