proposal -- add colorbrewer palettes as a color option for points, polygons and lines

[burritojustice]

trafficstars

add colorbrewer schemes to color:

layers:
    counties:
        polygon:
            color: OrRd[2]    

https://github.com/axismaps/colorbrewer/

hex is here, for reference:

https://github.com/google/palette.js/blob/master/palette.js#L931

[bcamper]

This is interesting. We would probably first prototype it via import-able building blocks and/or in Tangram Play before deciding if it made sense to include in the core. There have also been requests to be able to use D3's existing modules for palette/scale generation, so some general thought about the best way to enable this type of thing is in order.