title: nested series in highcharts drilldown
body: <p>I am trying to use <a href="http://www.highcharts.com/" rel="nofollow">highcharts.js</a>' drilldown with nested series. To keep things simple, I am using the official demo provided by highcharts.js:</p>
  
  <p><a href="http://jsfiddle.net/gh/get/jquery/1.7.2/highslide-software/highcharts.com/tree/master/samples/highcharts/drilldown/multi-series/" rel="nofollow">http://jsfiddle.net/gh/get/jquery/1.7.2/highslide-software/highcharts.com/tree/master/samples/highcharts/drilldown/multi-series/</a></p>
  
  <pre><code>drilldown: {
          series: [{
              id: 'republican-2010',
              data: [
                  ['East', 4],
                  ['West', 2],
                  ['North', 1],
                  ['South', 4]
              ]
  </code></pre>
  
  <p>I would like to modify this example to also compare election years in the drilldown. The official demo's drilldown only shows a single election year for each region (north, south, etc). I would like to have the same blue/black columns (election year) in the drilldown graphs.</p>
  
  <p>My attempts of nesting series in drilldowns are found here:</p>
  
  <p><a href="http://jsfiddle.net/draptik/bnvbsLd1/1/" rel="nofollow">http://jsfiddle.net/draptik/bnvbsLd1/1/</a></p>
  
  <pre><code>drilldown: {
    series: [{
      id: 'republican-2010',
      data: [{
        series: [{
          name: 'republican',
          data: [{
            name: 'north',
            y: 3
          }, {
            name: 'west',
            y: 3
          }, {
            name: 'east',
            y: 3
          }, {
            name: 'south',
            y: 3
          }]
        }, {
          name: 'democrat',
  </code></pre>
  
  <p>Basically I just tried to nest a series in the drilldown's series data array, but this does not work.</p>
  
  <p>Thankful for any pointer.</p>