This middleware comes before `app.router`, because it can't come after since the response will have already been sent. The tradeoff here is doing a little bit of duplicate logic that the router will do in favor of saving from having to do the more expensive work of exposing the YUI config and seed for requests which don't need it. Since a majority of requests will be for static assets, it seemed logical to me to avoid doing the expose work unless the router would be handling the request.