Fix bug divide by 0 by adding jiggle

src/link.js

@@ -22,7 +22,7 @@ export default function(links) {
     for (var k = 0, n = nodes.length, source, target, i, j, x, y, l; k < iterations; ++k) {
       // For each link
       for (i = 1; i < n; i++) for (j = 0; j < i; j++) {
-        // jiggle so it wont divide / multiply by zero after this
+        // jiggle so l won't be zero and divide by zero error after this
         source = nodes[i];
         target = nodes[j];
         x = target.x + target.vx - source.x - source.vx || jiggle();