Permit routing without invoking actions

I didn't see anything in the router blog post, but one of the commonly requested features in other web frameworks across various languages is to be able to use the router without invoking code.

For example, given a route `/foo/:bar` and a path `/foo/quux`, one would ideally be able to obtain some sort of identifier for the route and the mapping `bar` -> `quux`.

One initial problem would seem to be that there is no natural identifier for the route.