title: keep the extra whitespaces in display of pandas dataframe in jupyter notebook
body: <p>In jupyter notebook, extra whitespaces  in dataframe are removed. But sometime that is not preferred, e.g.</p>
  
  <pre class="lang-py prettyprint-override"><code>df=pd.DataFrame({'A':['a   b','c'],'B':[1,2]})
  df
  </code></pre>
  
  <p>The result I get:</p>
  
  <pre><code>|   | A   | B |
  |---|-----|---|
  | 0 | a b | 1 |
  | 1 | c   | 2 |
  </code></pre>
  
  <p>But I want:</p>
  
  <pre><code>|   | A     | B |
  |---|-------|---|
  | 0 | a   b | 1 |
  | 1 | c     | 2 |
  </code></pre>
  
  <p>Is it possible? Thanks</p>