title: Transition back to origin route
body: <p>So. I have a very simple problem, that should have a simple solution. I'm just not seeing it.</p>
  
  <p>In my ember app, I have a login route, and a link to this in the header. You click this, and get to a login form. When successfully logged in, I want to go back to the route displayed before the login form.</p>
  
  <p>Something like the following url sequence</p>
  
  <p>/post/209 - user clicks login<br>
  /login - user provides credentials, submits, and<br>
  /post/209 - is displayed</p>