Congrats for this gem. It's easy to use and really well documented.
I have a question: Would it be difficult to add the Toolbar (https://google-developers.appspot.com/chart/interactive/docs/gallery/toolbar)? As it's set in the draw method I can't add it once the chart has been rendered.
Any thoughts on how we could do that?
From the doc, the chart and toolbar can be created separately and they are not coupled together as dependencies (although they share the same source) - the toolbar's requirements are:
Therefore, you should still be able to render the toolbar even after the chart has been rendered although that functionality is not in the gem right now.
Having said that, this still might be a useful feature to add to the gem. I'll tag this as a feature.