title: How to define content-type with Code Igniter REST_Controller
body: <p>I'm working with the REST_Controller extended CI_Controller  and for some reason my requests are all coming back with a content-type of text/html instead of json. In my config, I have json set as the default format:</p>
  
  <pre><code>$config['rest_default_format'] = 'json';
  </code></pre>
  
  <p>My results are coming back as JSON, but the content-type isn't being set. Can anyone help with what I'm missing?</p>