title: capture a regex group in url with pagejs
body: <p>I want more than one optinal parameters in pagejs so I cannot go like this
  <code>
  /controller/action/:p1?/:p2?
  </code>
  because If p1 is not provided, value will be set to p1 instead of p2. So I went for this url form:
  <code>
  /controller/action/p1/:p1/p2/:p2
  </code>
  but this obligates the url to receive both param, so optional is now allowed,
  So I'd like to make both param prefix and param receiver optional within a regex group, going in this url way:
  <code>
  /controller/action(/p1/:p1)?(/p2/:p2)?
  </code>
  however it doesn't work, it sets a function to p1...</p>
  
  <p>any help on achieve this on pagejs ?</p>
  
  <p><a href="https://github.com/visionmedia/page.js" rel="nofollow">https://github.com/visionmedia/page.js</a></p>