title: drupal 8 error to render template twig with controller
body: <p>I am trying to render a template with my controller but does not work 
  it show me this error :</p>
  
  <blockquote>
    <p>LogicException: The controller must return a response (<h1>Hello Bob!</h1>  given). in Symfony\Component\HttpKernel\HttpKernel->handleRaw() (line 163 of core/vendor/symfony/http-kernel/Symfony/Component/HttpKernel/HttpKernel.php).</p>
  </blockquote>
  
  <p>My function : </p>
  
  <pre><code>public function helloAction($name) {
  $twigFilePath = drupal_get_path('module', 'acme') . '/templates/hello.html.twig';
  $template = $this-&gt;twig-&gt;loadTemplate($twigFilePath);
  return $template-&gt;render(array('name' =&gt; $name));
  }
  </code></pre>