title: Extend auth token without refreshing the page
body: <p>Users want to use my facebook app for many hours without refreshing the browser.<br>
  But token expires in 2 hours. Now I ask users to refresh the page but that's annoying.<br>
  I don't want to ask offline access permissions because it will scare some users.</p>
  
  <p>The best solution will be somehow "relogin" and get new token without refreshing the page.
  Is it possible?</p>