title: How would i use ->findTaggedServiceIds in a controller?
body: <p>the docs do it like this:</p>
  
  <pre><code>public function process(ContainerBuilder $container)
  {
      $taggedServices = $container-&gt;findTaggedServiceIds(
          'acme_mailer.transport'
      );
  }
  </code></pre>
  
  <p>But if i attempt to do this in a controller, i get method not found.</p>
  
  <pre><code>public function handlersAction() {
      $handlers = $this-&gt;container-&gt;findTaggedServiceIds(
          'quickship.handler'
      );
      return View::create($handlers);
  }
  </code></pre>
  
  <p>How do i access the ContainerBuilder in a controller?</p>