title: Searching for Chinese text throws UnicodeEncodeError
body: <p>I'm using <a href="https://github.com/bear/python-twitter" rel="nofollow">python-twiter</a> to search for tweets using Twitter's API and I have a problem with chinese terms. Here is a minimal code sample to reproduce the problem:</p>
  
  <pre><code># -*- coding: utf-8 -*-
  import twitter
  
  api = twitter.Api(consumer_key = "...", consumer_secret = "...",
                    access_token_key = "...", access_token_secret = "...")
  
  api.VerifyCredentials()
  print u"您说英语吗"
  r = api.GetSearch(term=u"您说英语吗")
  </code></pre>
  
  <p>I get this error:</p>
  
  <pre><code>您说英语吗
  Traceback (most recent call last):
            File "so.py", line 9, in &lt;module&gt;
      r = api.GetSearch(term=u"您说英语吗")
    File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/python_twitter-0.8.7-py2.7.egg/twitter.py", line 2419, in GetSearch
      json = self._FetchUrl(url, parameters=parameters)
    File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/python_twitter-0.8.7-py2.7.egg/twitter.py", line 4041, in _FetchUrl
      url = req.to_url()
    File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/oauth2-1.5.211-py2.7.egg/oauth2/__init__.py", line 440, in to_url
      urllib.urlencode(query, True), fragment)
    File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib.py", line 1337, in urlencode
      l.append(k + '=' + quote_plus(str(elt)))
  UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-4: ordinal not in range(128)
  </code></pre>