title: Google Sign in delete cookies on signOut
body: <p>I'm validating the user's account if he is allowed to sign in.
  When he isn't allowed, he will be signed out with:
  <code>gapi.auth2.getAuthInstance().signOut()</code> </p>
  
  <p>The problem is when he presses the sign in button again, the account chooser won't appear.
  It just uses the old cached account and he will be immediately signed out again.</p>
  
  <p>How can I delete the cookies, in order to show the account chooser again?</p>