title: Tooltips disappear after zoom in/out when using matplotlib mpld3
body: <p>I have a matplotlib figure with tooltips on the point markers:
  <img src="https://i.stack.imgur.com/s9s9n.jpg" alt="enter image description here"></p>
  
  <p>And the zoom in/out is working:</p>
  
  <p>However after the zoom in/out is performed the tooltips no longer function: and even restoring the original (non-zoomed) size they do not come back.</p>
  
  <p><img src="https://i.stack.imgur.com/54nAg.jpg" alt="enter image description here"></p>