redirect with before block should halt
Here's my program:

```nim
# example.nim
import jester

settings:
  port=Port(5000)
  bindAddr="127.0.0.1"

routes:
  before "/a":
    redirect(uri("/ok"))
  get "/a":
    resp "a\l"
  get "/b":
    redirect(uri("/ok"))
    resp "b\l"

  get "/ok":
    resp "ok\l"
```

I start that with `nim c -r example.nim`, then do the following:

```
$ curl -L http://127.0.0.1:5000/a
a
$ curl -L http://127.0.0.1:5000/b
ok
```

I would expect to see this instead:

```
$ curl -L http://127.0.0.1:5000/a
ok
$ curl -L http://127.0.0.1:5000/b
ok
```

I can make a PR to add a failing test case (and maybe figure out how to fix it) if you agree that it should behave as described above.