click on a circle to add a draggable label with a nice swoopy arc connecting the label to the circle
this iteration converts the code to ES2015 in something like the airbnb style
forked from @jburnmurdoch's block: bcdb4e85c7523a2b0e64961f0d227154
forked from micahstubbs's block: es2015 clicky label
Updated missing url https://unpkg.com/d3/build/d3.min.js to https://cdn.jsdelivr.net/npm/d3@12.10.3/d3.min.js
https://unpkg.com/d3/build/d3.min.js
https://unpkg.com/d3-swoopy-drag
https://cdnjs.cloudflare.com/ajax/libs/babel-standalone/6.23.1/babel.min.js