title: tag facebook friends python sdk GraphApi in put_photo
body: <p>I would to post pictures and tag with frieds.</p>
  
  <pre><code>graph = facebook.GraphAPI(self.cfg['access_token'])
  tags = [{"tag_uid": "1234567890", "x": 0, "y": 0}, {"tag_uid": "0001234567890", "x": 0, "y": 0}]
  graph.put_photo(image=open(str(file), 'rb'), message='Pictures test', **{'tags': tags})
  </code></pre>
  
  <p>but i've this error </p>
  
  <pre><code>facebook.GraphAPIError: (#100) param tags must be an array.
  </code></pre>