title: Extending Middleman to handle a new filetype (.JADE)
body: <p>I'd like to add .jade support to Middleman. I don't need to use any of jade's dynamic features, but I'd like to compile my app in middleman rather than with my own messy compile script.</p>
  
  <p>What is the simplest way to add a new file type to Middleman?</p>