Fix typo

src/link.js

@@ -15,7 +15,7 @@ export default function() {
       nodes,
       stableVelocity = 0,
       stableVeloHandler = null,
-      latestVelocityDiff = 0
+      latestVelocityDiff = 0,
       iterations = 1;
 
   function force(alpha) {

src/stress.js

@@ -7,7 +7,7 @@
 export function getStress(nodes, distance) {
   let sumDiffSq = 0
   let sumLowDDistSq = 0;
-  for (let j = nodes.length-1; j >= 1; j++) {
+  for (let j = nodes.length-1; j >= 1; j--) {
     for (let i = 0; i < j; i++) {
       let source = nodes[i], target = nodes[j];
       let lowDDist = Math.hypot(target.x - source.x, target.y - source.y);