title: Intercept Route Request with Angular 2 Router
body: <p>With the Angular 2 Router I'd like to capture an event when a route is requested to be activated.  In Angular 1.x I used $locationChangeSuccess, and then checked to see if the user was logged in or not.  </p>
  
  <p>I need to do something similar with Angular 2, so I can redirect a user to a login screen if they aren't yet authenticated.  </p>