vega-lite testing

https://cdnjs.cloudflare.com/ajax/libs/vega/3.0.0-beta.25/vega.js

https://cdnjs.cloudflare.com/ajax/libs/vega-lite/2.0.0-alpha.7/vega-lite.js

https://cdnjs.cloudflare.com/ajax/libs/vega-embed/3.0.0-beta.7/vega-embed.js