title: jQuery .attr() does not set custom attribute and value
body: <p>I'm simply setting a custom attribute in the document.ready function in the following way:</p>
  
  <pre><code>$(document).ready(function(){
      $("div.para, pre.screen, div.figure, pre.programlisting").attr("data-test-ID", "hello");
  });
  </code></pre>
  
  <p>When I reload the HTML and look at the source, there is no trace of such attribute anywhere. Any ideas? I'm really stuck on this and can't figure it out.</p>