Create year-based sponsor directory

[mattstratton]

This will allow for different sponsors each year just in case the sponsor logos change YOY in order to prevent anachronistic sponsor logos on older events.

This is not needed eventually - see #113 (when resolved) to see how we might do it with a query to check from the current year being used.

Not an immediate concern.

[mattstratton]

This is actually lumped into #133, so this issue can be closed.