title: Destroy scope in $destroy event
body: <p>Found this code one of the directives in a project I'm working on:</p>
  
  <pre><code>element.on('$destroy', function () {
      scope.$destroy();
  });
  </code></pre>
  
  <p>Is this code needed? Or can I remove it? Isn't scope destroyed when directive is destroyed?</p>