title: setgroup() in notification not working
body: <p>I'm tring to create notification group, this is my code:</p>
  
  <pre><code> // Build the notification, setting the group appropriately
   Notification notif = new NotificationCompat.Builder(getApplicationContext())
            .setContentTitle("New mail from " + 1)
            .setContentText("cv")
            .setSmallIcon(R.drawable.rh_logo)
            .setStyle(new NotificationCompat.InboxStyle()
              .addLine("Alex Faaborg   Check this out")
              .addLine("Jeff Chang   Launch Party")
              .setBigContentTitle("2 new messages")
              .setSummaryText("johndoe@gmail.com"))
            .setGroup(GROUP_KEY_EMAILS)
            .setGroupSummary(true)
            .build();
  
   // Issue the notification
  
  
  
   NotificationManager notificationManager = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
   notificationManager.notify(++NOTIFICATION_ID, notif);
  </code></pre>
  
  <p>When I run the app, and send notification messages, they do not show in group.
  Can someone explain me what I need to change?</p>