Inspired by this tweet
forked from tomshanley's block: Sankey with circular links and self-linking nodes
forked from tomshanley's block: Sankey with Minard labels on the links
forked from tomshanley's block: Sankey with Minard dots for different link types
https://d3js.org/d3.v4.min.js
https://d3js.org/d3-scale-chromatic.v1.min.js