title: Show "loading" animation on button click
body: <p>I want to do something very simple.
  I have one button in my page.</p>
  
  <pre><code>&lt;form action="/process" method="POST"&gt;
     &lt;input class="btn btn-large btn-primary" type="submit" value='Analyze Topics'&gt;
      &lt;/form&gt;
  </code></pre>
  
  <p>Now what I want is when the user presses this submit button. It shows that "loading" gif animation until it gets the response from server.</p>
  
  <p>But I have been struggling since long time.</p>
  
  <p>How do I implement this?</p>