title: Facebook Messenger webhook setup, but not triggered
body: <p>So I'm trying to setup a bot for the new Facebook Messenger API.</p>
  
  <p>I'm following <a href="https://developers.facebook.com/docs/messenger-platform/quickstart" rel="noreferrer">the quickstart</a>.</p>
  
  <p>I setup the webhook ok, and see it in my webhooks,</p>
  
  <p>I called this:</p>
  
  <pre><code>https://graph.facebook.com/v2.6/me/subscribed_apps?access_token=%3Ctoken%3E
  </code></pre>
  
  <p>and it did not throw any errors,</p>
  
  <p>But when I go to the Page that I generated the access token on, and send a message, it does not call my webhook.
  I check the httpaccess, and it does not call it.</p>
  
  <p>Any way to debug this or any ideas?</p>
  
  <p>Also, one thing I'm still puzzled over is how to support managing multiple pages from one Facebook  app? Anyone know the answer to this, or do you need to create anew app and get permission for every page?</p>