title: Python nltk.clean_html not implemented
body: <p>I have been trying to use</p>
  
  <pre><code>myNews=urlopen(url).read()    
  myNews=nltk.clean_html(myNews)
  </code></pre>
  
  <p>I get the following error:</p>
  
  <p>File "/usr/local/lib/python2.7/dist-packages/nltk-3.0.0-py2.7.egg/nltk/util.py", line 346, in clean_html
      raise NotImplementedError ("To remove HTML markup, use BeautifulSoup's get_text() function")
  NotImplementedError: To remove HTML markup, use BeautifulSoup's get_text() function</p>
  
  <p>When I look to the file util.py, I can see that it is not implemented:</p>
  
  <pre><code>def clean_html(html):
      raise NotImplementedError ("To remove HTML markup, use BeautifulSoup's get_text() function")
  </code></pre>
  
  <p>Should it not be implemented?</p>