Control bar text

There is a bug, causing chart.stacked(true) to be ineffective, and user has to click two times in order to update the chart:
image

Click Stacked, then Grouped, then Stacked, and graph updates.
The issue is most likely here: https://github.com/ividata/nvd3/blob/a0544ea651371590dd9aa2dc2490cdc5150779bf/src/models/multiBarHorizontalChart.js#L36, the disabled is not updated when we programmatically set stacked - only when user clicks.