title: d3 circle pack layout for bubble chart - how can I enable bubble dragging in pack layout?
body: <p>I am using d3.layout.pack for rendering bubble chart. 
  Code is here : <a href="http://bl.ocks.org/mbostock/4063530" rel="nofollow">http://bl.ocks.org/mbostock/4063530</a></p>
  
  <p>Chart renders properly, now I want to make the inner bubbles draggable. so user can move the circles inside the main outer circle.</p>
  
  <p>I did same with help of force layout but not able to do it with pack layout.</p>