title: Bokeh server and on.click (on.change) doing nothing
body: <p>I am trying to get Bokeh server to print out, however all I get is an instance running on <a href="http://localhost:5006/?bokeh-session-id=default" rel="nofollow">http://localhost:5006/?bokeh-session-id=default</a> with the radio buttons. When I click the buttons nothing happens. Is there something I am missing?</p>
  
  <pre><code>from bokeh.models.widgets import RadioButtonGroup
  from bokeh.plotting import figure, show, output_server
  
  
  def my_radio_handler():
      print 'Radio button option selected.'
  
  
  radio_button_group = RadioButtonGroup(
          labels=["Option 1", "Option 2", "Option 3"], active=0)
  
  radio_button_group.on_click(my_radio_handler)
  
  output_server()
  
  show(radio_button_group)
  </code></pre>