title: Switch user or re authenticate with Instagram
body: <p>Following the <a href="http://instagram.com/developer/authentication/">Instagram documentation</a> I'm able to authenticate a user and retrieve an access_token easily</p>
  
  <p>But now I want to change of Instagram account which is impossible since the browser automatically call my callback URL because I'm already signed in with an account (there is no login / authorization form again)</p>
  
  <p>To explain what happen here is the authenticate / authorization flow :</p>
  
  <ol>
  <li>Open a browser asking user to log and authorize</li>
  <li>User fill up form and submit <strong>(this step is skipped when user is already signed in !)</strong></li>
  <li>Browser redirect to callback URL</li>
  </ol>
  
  <p>You see step 2 is skipped so we can't login with another user</p>
  
  <p>Does the Instagram have a parameter to force relogin ?</p>