title: Manually change x range for Bokeh plot
body: <p>So I'm trying to create a Bokeh plot for which I would like to be able to manually adapt the range of the X-Axis with a slider. 
  Being a newbie I've only managed to get this far and despite researching this subject I haven't been able to solve this problem.</p>
  
  <p>Here my code:</p>
  
  <pre><code>from bokeh.layouts import column
  from bokeh.models import CustomJS, ColumnDataSource, Slider
  from bokeh.plotting import Figure, output_file, show
  output_file("test.html")
  x = [x*0.5 for x in range(0, 200)]
  y = x
  source = ColumnDataSource(data=dict(x=x, y=y))
  plot = Figure(plot_width=600, plot_height=400, x_range=(0, 100))
  plot.line('x', 'y', source=source, line_width=2, line_alpha=0.75)
  callback = CustomJS(args=dict(x_range=plot.x_range), code="""
      var start = cb_obj.value
      x_range.set({"start": start, "end": start+10})
  """)
  slider = Slider (start=0, end=90, value=20, step=10)
  slider.js_on_change('value', callback)
  layout = column(slider, plot)
  show(layout)
  </code></pre>
  
  <p>My biggest problem is to understand how I connect the CustomJS to my plot.
  I would gladly appreciate your help.</p>