code: public URLNormalizer removeDuplicateSlashes() {
          String urlRoot = HttpURL.getRoot(url);
          String path = toURL().getPath();
          String urlRootAndPath = urlRoot + path;
          String newPath = path.replaceAll("/{2,}", "/");
          String newUrlRootAndPath = urlRoot + newPath;
          url = StringUtils.replaceOnce(url, urlRootAndPath, newUrlRootAndPath);
          return this;
      }
docs: <p>Removes duplicate slashes.  Two or more adjacent slash ("/")
  characters will be converted into one.</p>
  <code>http://www.example.com/foo//bar.html
  &rarr; http://www.example.com/foo/bar.html </code>
  @return this instance