title: Kohana 3.2 request->headers['Content-Type'] keeps failing
body: <p>This won't work in Kohana 3.2 for some reason:</p>
  
  <pre><code>$this-&gt;request-&gt;headers['Content-Type'] = 'text/xml';
  </code></pre>
  
  <p>Has this changed since Kohana 3.1?</p>