title: Get d3 v4 zoom and drag working together - simple example
body: <p>Consider <a href="https://bl.ocks.org/puzzler10/d98ca2993392609d55a9d4ec9d31cbd3" rel="nofollow noreferrer">this code example</a> in d3 version 4. </p>
  
  <p>There's a number of yellow circles overlaid on top of a black background. </p>
  
  <p>I can drag the circles around with my mouse. I can also zoom in and out using the mousewheel, providing my mouse is not over a circle. </p>
  
  <p>There's two problems that I'd like to fix: </p>
  
  <ul>
  <li>I would like to zoom in when I hit the scroll wheel while I am moused over a circle. </li>
  <li>Drag and drop is incorrect when I am zoomed in or out of the graph - the circles don't follow the mouse. </li>
  </ul>