title: How to import Bokeh palettes
body: <p>How to use the <a href="http://bokeh.pydata.org/en/latest/docs/reference/palettes.html#d3-palettes" rel="noreferrer">D3 Palettes</a> in Bokeh?
  I tried importing this way but I get an unresolved reference error message</p>
  
  <pre><code>from bokeh.palettes import Category20
  </code></pre>
  
  <p>Bokeh version:</p>
  
  <pre><code>print bokeh.__version__
  
  0.11.1
  </code></pre>