title: lowercase with Jade template
body: <p>I'm using jade in a <code>nodejs</code> project</p>
  
  <p>Can't find how to define filters</p>
  
  <p>I have categories that i want to display in a select box, lowercase option values and uppercase option text</p>
  
  <pre><code>select
    each cat in categories
      option(value="lowercase(#{cat})") uppercase(#{cat})
  </code></pre>
  
  <p>any idea ?</p>