Recalculate regions affected when filters are used on the homepage

The CA region map on the homepage of water.openoakland.org sticks at the statewide no filter data level but it would be cool if we could dynamically (or pregenerate) the regions color coded by severity to match the data in the selected filters.

also change the colors of the regions to match the designs here https://www.figma.com/file/zrPWQpnZyo0KI54BC1V0fc/CA-Water?node-id=0%3A1