title: JSONRenderer won't serialize: b'{"id":"11122211133311"}' is not JSON serializable
body: <p>I've problem with serializing object using JSONRenderer.</p>
  
  <p>I'm using <code>django-rest-framework</code> and I've serialized object:</p>
  
  <pre><code>  pk = kwargs['pk']
    tube = Tube.objects.get(id=pk)
  
    serialized_tube = TubeSerializer(tube)
  </code></pre>
  
  <p><code>serialized_tube.data</code> looks like this:</p>
  
  <blockquote>
    <p>{'id': '11122211133311'}</p>
  </blockquote>
  
  <p>Unfortunately I can't serialize this using JSONRenderer, because the code</p>
  
  <pre><code>  tube_json = JSONRenderer().render(serialized_tube.data)
    return Response(tube_json)
  </code></pre>
  
  <p>gives following error</p>
  
  <blockquote>
    <p>b'{"id":"11122211133311"}' is not JSON serializable</p>
  </blockquote>
  
  <p>whereas</p>
  
  <pre><code>  tube_json = json.dumps(serialized_tube.data)
    return Response(tube_json)
  </code></pre>
  
  <p>works well...</p>
  
  <p>I'm using Python3.4.3</p>