[Solved]-Pie chart with drilldown not working-Highcharts

I finally solved it (sorry I had to answer my own question), thanks to Pawel Fus's enlightening comment :)
First I added the drill down module:

    <script src="http://code.highcharts.com/modules/drilldown.js"></script>

Next I followed this answer and added some code to the highcharts-ng lib:
Highcharts-ng with drilldown

Finally I put the drilldown attribute under the option attribute as mentioned here:
https://github.com/pablojim/highcharts-ng/pull/145

Here is the final woorking plunker:
http://plnkr.co/edit/S1B9Q9e1yen0QgmKt2ri