code: public URLNormalizer removeWWW() {
          String host = toURL().getHost();
          String newHost = StringUtils.removeStartIgnoreCase(host, "www.");
          url = StringUtils.replaceOnce(url, host, newHost);
          return this;
      }
docs: <p>Removes "www." domain name prefix.</p>
  <code>http://www.example.com/ &rarr; http://example.com/</code>
  @return this instance