title: How to add an 'arrow' to the tooltip using the nvd3 tooltip
body: <p>Is there any way I can add an arrow next to the nv.tooltip hover like the way the bootstrap has??</p>
  
  <p>Eg: Bootstrap tooltip/popover</p>
  
  <p><img src="https://i.stack.imgur.com/Dmk3W.png" alt="enter image description here"></p>
  
  <p>nvd3 tooltip:</p>
  
  <p><img src="https://i.stack.imgur.com/aYsRM.png" alt="enter image description here"></p>