title: Add regex rule to remove "www." on existing expression
body: <p>With the help <a href="https://stackoverflow.com/a/8498629/1417223">from this answer</a> I'm getting clean domain names from urls in strings, like the following:</p>
  
  <pre><code>url = "http://www.stackoverflow.com/questions/ask"  
  var matches = url.match(/^https?\:\/\/([^\/?#]+)(?:[\/?#]|$)/i);  
  return matches ? matches[1] : url;
  &gt;&gt; "www.stackoverflow.com"
  </code></pre>
  
  <p>I would like to remove the subdomain "www" (and the following dot) as well though, if existing. How would I change the above expression to accomplish this?</p>