Added materialDesign attribute to enable new charts.

[zmoshansky]

#30 implementation for the charts that have a Material Design Beta version. (This is an updated #39 PR.)

All original charts work fine.

The new material-design charts on the demo page sometime have an issue rendering. This can be resolved by chart._chartObject = null && chart.drawChart(). I believe it's an issue with the timing of the loading, but since the code is obfuscated there's nothing a community contribution can do.

Anecdotally, using just a couple material-design charts on a single page of an SPA renders correctly every time. (#ItWorksOnMyMachine)

Given that these are marked as BETA, it would be great if people could opt-in to using the feature and the known hiccups until someone with access to the source can diagnose the root cause of the issue.

[wesalvaro]

So I tried attacking this tonight but it seems that the google.load result for the new packages isn't right as I was unable to get the charts to render correctly or consistently in the demo.

Using the new recommended loader google.charts.load from https://www.gstatic.com/charts/loader.js works, but cannot be called more than once (?) so it requires loading all of the chart packages for our purposes.

I'll try to track down a better solution, but it's a bummer.

[rslawik]

I believe the material design charts are available with type="md-bar" or type="md-line".
JS bin demo