title: parseerror when getting XML via jQuery AJAX
body: <p>I want to pull an RSS feed via jQuery AJAX, but every time I do, I get a parsererror. My feed is relatively complex (using CDATA and custom namespaces), so I tried stripping down the document returned (along with a million other combinations), but even with an extremely simple document, it still fails. This is my AJAX code:</p>
  
  <pre><code>$.ajax({
      type: 'GET',
      url: ...,
      dataType: 'xml',
  
      success: function(xml) {
          ...
      },
  
      error: function(xhr, textStatus, error) {
          console.log('status: ' + textStatus);
          console.log(xhr.responseText);
          showError('an unknown error occurred while trying to fetch the feed: ' + xhr.status);
      }
  });
  </code></pre>
  
  <p>Console output:</p>
  
  <pre><code>status: parsererror
  &lt;?xml version="1.0"?&gt;
  
  &lt;rss version="2.0"&gt;
      &lt;channel&gt;
          &lt;title&gt;title&lt;/title&gt;
          &lt;link&gt;link&lt;/link&gt;
          &lt;description&gt;desc&lt;/description&gt;
  
          &lt;lastBuildDate&gt;build date&lt;/lastBuildDate&gt;
          &lt;generator&gt;gen&lt;/generator&gt;
      &lt;/channel&gt;
  &lt;/rss&gt;
  </code></pre>