Score recalculation

Adds a Rake task to recalculate scores for the current competition. This task will be scheduled to run nightly.

Tweaks the score calculator to ignore trips logged in the future, which should eliminate participation percentages being greater than 100%. Any future trips will be picked up by the daily Rake task, on the day they were logged.
I think this is too simplistic. Since we're calculating percentage based on the current week, we should allow any future rides for the current week. We should only block rides for next week.