The routing in 0.4.0 leads to Http400 errors instead of Http404
I decided to set up a small app to start trying to learn jester ([source](https://bitbucket.org/PrimordialHelios/nim-app/src)). Using the latest version of Jester and the new `router` syntax, Jester is responding with an Http400 instead of an Http404 when a resource is requested that can't be found.

For instance, my routing looks something like this:

```nim
router v0Api:
    get "/add":
        resp "This is the add page"

router apiRouter:
    extend v0Api, "/v0"

routes:
    error Http404:
        resp Http404, "Looks you took a wrong turn somewhere."
    extend apiRouter, "/api"
    get "/":
        resp "test"
```

The `/api/v0/add` and `/` pages work just fine, but trying to request any resource that doesn't exist (such as `/foo`, `/api/bar`, etc.) returns Http400.