a now-successful attempt to draw links with canvas paths so that the end of each link overlaps perfectly with the center of an svg circle we use to represent a node.
thanks to @enjalot for pointing out that the CSS body { margin: 0; } would do the trick.
a clue: somehow the canvas links layer lines up nicely with the svg nodes layer in the iframe on bl.ocks.org but doesn't at all when it's all by itself on the page ๐ค
a fork of Blocks Graph I Readme Mentions
a simpler example of this canvas for links, svg for nodes network drawing technique is the bl.ock Ch. 11, Fig. 10 - D3.js in Action from emeeks