Use d3.map in NewStylePlot. Also clean up some other code slightly
Merge pull request #893 from palantir/develop

Retarget #884 to develop. Use d3 map instead of object in new style plot.
Merge pull request #895 from palantir/use-d3-map-instead-of-object-in-new-style-plot

Use d3 map instead of object in new style plot