title: Save unicode in redis but fetch error
body: <p>I'm using mongodb and redis, redis is my cache.</p>
  
  <p>I'm caching mongodb objects with redis-py:</p>
  
  <pre><code>obj in mongodb: {u'name': u'match', u'section_title': u'\u6d3b\u52a8', u'title': 
  u'\u6bd4\u8d5b', u'section_id': 1, u'_id': ObjectId('4fb1ed859b10ed2041000001'), u'id': 1}
  </code></pre>
  
  <p>the obj fetched from redis with hgetall(key, obj) is:</p>
  
  <pre><code>{'name': 'match', 'title': '\xe6\xaf\x94\xe8\xb5\x9b', 'section_title': 
  '\xe6\xb4\xbb\xe5\x8a\xa8', 'section_id': '1', '_id': '4fb1ed859b10ed2041000001', 'id': '1'}
  </code></pre>
  
  <p>As you can see, obj fetched from cache is str instead of unicode, so in my app, there is error s like :'ascii' codec can't decode byte 0xe6 in position 12: ordinal not in range(128)</p>
  
  <p>Can anyone give some suggestions? thank u</p>