title: NVD3.js highlight graph points at mouseover event
body: <p>How do I highlight points on a linechart when moving my mouse over another graph.</p>
  
  <p>I need information from one chart when moving my mouse over it to send the selected data to another chart to highlight the points in the other chart.</p>
  
  <p>e.g. chart 1 has a mouseover at x:3 y:5. It fires an event to highlight another charts line. 
  Then at chart 2 you highlight the x:3 y:5 value.</p>