title: Fenced code block not highlighted properly
body: <p>In Jekyll, when I set the Markdown converter to kramdown and <code>bundle exec jekyll serve</code>, this fenced code block</p>
  
  <pre><code>```javascript
  function hey(name) {
      return 'Hey ' + name;
  }
  
  console.log(hey('Brienna'));
  ```
  </code></pre>
  
  <p>renders like this:
  <img src="https://cloud.githubusercontent.com/assets/9706870/13385355/dc8213c8-de6d-11e5-87b9-980ef5fefb14.png" alt="kramdown"></p>
  
  <p>This happens no matter what I do. I've tried setting the <code>input: GFM</code> option, but it doesn't make a difference whether or not it's included.</p>
  
  <p>However, when I set the Markdown converter to Redcarpet, the same code block renders like this:
  <img src="https://cloud.githubusercontent.com/assets/9706870/13385386/0eaefc9e-de6e-11e5-83b6-7fefc2a07b9d.png" alt="1 appearance"></p>
  
  <p>This is what I want to see! But I don't want to use Redcarpet. I want to use kramdown. </p>
  
  <p>As you can see from the rendered HTML below, the code block gets highlighted. I'm using a CSS stylesheet for Pygments, which Rouge is supposed to be able to work with. I noticed that the <code>div</code>'s class changed between Markdown converters. With kramdown, its class is <code>.highlighter-rouge</code>, whereas with Redcarpet, its class is just <code>highlight</code>. Do I need to manually modify the CSS if switching between Markdown converters? </p>
  
  <p>Kramdown: </p>
  
  <p><img src="https://cloud.githubusercontent.com/assets/9706870/13385428/81ca0d4a-de6e-11e5-8656-920325316af2.png" alt="kramdown elements"></p>
  
  <p>Redcarpet: </p>
  
  <p><img src="https://cloud.githubusercontent.com/assets/9706870/13385184/fdd3afb6-de6b-11e5-99f8-2eba1b3b7c8a.png" alt="1 elements"></p>