draggable not working

I recently started using c3 and loving it so far. I have a basic line chart and want to have the points draggable. So according to the docs, I added `selection: { draggable: true }` in my data as follows:

```
var chart = c3.generate({
bindto: '#chart-' + this.toolId,
data: {
columns: [column1, column2],
selection: { draggable: true }
}
});
```

but nothing changed. I also tried setting the option in one of the examples on c3 website. It's not working there as well. Am I missing something here? Any help is really appreciated. Thanks.

The functionality I want is to be able to drag the data points and the line adjusts itself accordingly. For example, http://bl.ocks.org/stepheneb/1182434