title: documenting private methods in ruby rails
body: <p>I can use rdoc to generate Darkfish documentation for rails code including my private methods, as in</p>
  
  <pre>
  rdoc app --all
  </pre>
  
  <p>but when I use the built in rake task:</p>
  
  <pre>
  bin/rake doc:app
  </pre>
  
  <p>it won't accept the "--all" option.</p>
  
  <p>Is there an option for this?</p>