title: gapi is not defined - Google sign in issue with gapi.auth2.init
body: <p>I'm trying to implement Google Sign In and retrieve the profile information of the user. 
  The error is: Uncaught ReferenceError: gapi is not defined. Why is that?</p>
  
  <pre><code>&lt;!doctype html&gt;
  &lt;html&gt;
  &lt;head&gt;      
  &lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"&gt;&lt;/script&gt;
  &lt;script src="https://apis.google.com/js/platform.js" async defer&gt;&lt;/script&gt;
      &lt;script type="text/javascript"&gt;
      $(function(){
          gapi.auth2.init({
              client_id: 'filler_text_for_client_id.apps.googleusercontent.com'
          });
      });
  &lt;/head&gt;
  &lt;body&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>