anchor.diff:    <li><a href="http://apple.com">Apple</a></li>
   </ul>
   ```
  +[.selector]
   ```scala
   "a [href]" #> "http://mozilla.org"
   ```
  
positive.code:   <li><a href="http://apple.com">Apple</a></li>
  </ul>
  ```
  ```scala
  ".name" #> user.name
  ```
  
negative.code:   <li><a href="http://apple.com">Apple</a></li>
  </ul>
  ```
  [.selector]
  ```scala
  "a *" #> "Mozilla" &
  "a [href]" #> "http://mozilla.org" &
  