RouterBuilder improvements

Issues #3 #4 #5

#3

router {
  route('/members') {
     get { yield members.all }
     get('/:memberId') { yield members.find(request.params['id']) }
  }
}

#4
extensions are executed in the order they're declared (and possibly after the actual handler is called)

#5

router {
  route('/members') {
    options | post | get {
       response << 'method of: options or post or get'
    }
  }
}