title: changing id/URL slug in rails 3 app using mongoid
body: <p>Currently in my rails app, records are located at URLs like:</p>
  
  <p><a href="http://www.mysite.com/items/fecffe6aa299a6050274ed22" rel="nofollow">http://www.mysite.com/items/fecffe6aa299a6050274ed22</a></p>
  
  <p>but instead I'd like them to be going to something like:</p>
  
  <p><a href="http://www.mysite.com/items/item-title-here" rel="nofollow">http://www.mysite.com/items/item-title-here</a></p>
  
  <p>any ideas for how I can accomplish this?</p>