title: How do I add hover highlighting to Bokeh Step Chart
body: <p>I am working to try and replicate code similar to the second graph from this <a href="http://fortune.com/fortune500/visualizations/?iid=recirc_f500landing-zone1" rel="nofollow noreferrer">http://fortune.com/fortune500/visualizations/?iid=recirc_f500landing-zone1</a></p>
  
  <p>There is the default Step Chart in Bokeh, but it does not want to let me add glyphs.</p>
  
  <p>I would like code something like this</p>
  
  <pre><code>from bokeh.charts import Step, show, output_file
  
  # build a dataset where multiple columns measure the same thing
  data = dict(
         stamp=[.33, .33, .34, .37, .37, .37, .37, .39, .41, .42,
                .44, .44, .44, .45, .46, .49, .49],
         postcard=[.20, .20, .21, .23, .23, .23, .23, .24, .26, .27,
                   .28, .28, .29, .32, .33, .34, .35]
     )
  
  # create a step chart where each column of measures receives a unique color and dash style
  step = Step(data, y=['stamp', 'postcard'],
          dash=['stamp', 'postcard'],
          color=['stamp', 'postcard'],
          title="U.S. Postage Rates (1999-2015)",
          ylabel='Rate per ounce', legend=True)
  
  selected_line = Line(line_alpha=1, line_color="firebrick")
  nonselected_line = Line(line_alpha=0.2, line_color="blue")
  
  step.add_glyph(data,
             step,
             selection_glyph=selected_line,
             nonselection_glyph=nonselected_line
  )
  
  output_file("steps.html")
  
  show(step)
  </code></pre>
  
  <p>I have tried each way from this page <a href="http://docs.bokeh.org/en/latest/docs/user_guide/styling.html#selected-and-unselected-glyphs" rel="nofollow noreferrer">http://docs.bokeh.org/en/latest/docs/user_guide/styling.html#selected-and-unselected-glyphs</a> is there a way to build this plot without the Chart library?</p>