title: Plugin documention with RDoc in Rails 3
body: <p>I'm writing a Rails 3 plugin and I'm using Engines. I have and app/ folder in my plugin with controller, models and views.</p>
  
  <p>The problem is that when I want to generate documentation with RDoc it won't go into the app/ folder to parse the files in there. Is there an option I have to pass to it so it will know where to search for them?</p>