title: Issue on Disabling (Not Displaying) Highcharts Drill-up Back Button
body: <p>I have my own custom btton to dril up highchart chart by using <code>chart.drillUp();</code> function but I still getting highchart built in drill up button so I tried to disable default button by setting it's text to empty string as: </p>
  
  <pre><code>Highcharts.setOptions({
      lang: {
          drillUpText: ''
      }
  });
  </code></pre>
  
  <p><a href="http://jsfiddle.net/Behseini/u4ao5z6f/" rel="nofollow">Demo</a></p>
  
  <p>but still there is a small button in the chart in drill-down. Can you please let me know how to get rid of it completely?</p>