Deferred Loading & Accessibility

With the way it was set up before, the entire page would need to wait for Google APIs to load before loading. Now the the plugin will wait until Google API is loaded before firing and converting tables to charts.

I've also removed the need for 3 <script> tags and reduced to 1. The Google API gets loaded via jQuery's .getScript() and the init happens automatically after that loads.

Also added aria attributes for accessiblity. This was the primary reason I was drawn to gvCharts. The table is still present and can be used as alternate content.