Only execute queries on 404

[jmfederico]

I'm using this gem, very helpful, but noticed that it executes the queries for every request rails receives, which means an extra DB query for every request.

I think it could be made so that it only executes when a 404 is found (no route matches), and then, and only then look for a redirect rule, this would reduce the number unnecessary of DB queries.

I'm not in a position to code this, I'm just learning Ruby, Rails and Rack work.