title: Stop zooming at a certain level in Bokeh WheelZoomTool
body: <p>Is there a way to stop zooming in at a certain x axis level? I am using a <code>xwheel_zoom</code> tool in my dashboard with a <code>datetime</code> x-axis. This is the tick format I'm using:</p>
  
  <pre><code>p.xaxis.formatter=DatetimeTickFormatter(
              microseconds=["%H:%M:%S:%3Nms"],
              milliseconds=["%H:%M:%S:%3Nms"],
              seconds=["%H:%M:%S"],
              minsec=["%H:%M:%S"],
              minutes=["%H:%M:%S"],
              hourmin=["%H:%M:%S"],
              hours=["%H:%M:%S"],
              days = ['%m/%d', '%a%d'],
              months = ['%m/%Y', '%b %Y'],
              years = ['%Y']
              )
  </code></pre>
  
  <p>Is it possible to just stop the zooming in (like being deactivated when the user scrolls) when the datetime reaches a millisecond scale? My chart makes sense only up to seconds, and I don't want the user to be able to zoom in forever!</p>