title: word2vec getting encode error
body: <p>I am getting the following error when i execute my code</p>
  
  <pre><code>Traceback (most recent call last):
    File "test.py", line 21, in &lt;module&gt;
      print model.most_similar(positive=['男人'])
    File "/usr/local/lib/python2.7/dist-packages/gensim/models/word2vec.py", line 660, in most_similar
      raise KeyError("word '%s' not in vocabulary" % word)
  KeyError: "word '\xe7\x94\xb7\xe4\xba\xba' not in vocabulary"
  </code></pre>
  
  <p>My code here</p>
  
  <pre><code> # -*- coding: utf8 -*    
      from gensim.models import word2vec
      import logging
  
  logging.basicConfig(format='%(asctime)s : %(levelname)s : %(message)s', level=logging.INFO)
          sentences = word2vec.Text8Corpus('/tmp/text8')
          model = word2vec.
      Word2Vec(sentences, size=200)
          model.most_similar(['男人'])
  </code></pre>