Add entry to select between normal and tweaked Link Force

- Tweaked link force should initialize and perform the calculation a tiny bit faster (maybe insignificant)

src/link.js

@@ -4,10 +4,12 @@ import jiggle from "./jiggle";
 /**
  * Modified link force algorithm
  * - ignore alpha
- * - removed location prediction, and bias
+ * - removed bias
  * - modified strength calculation
  * - removed other unused functions
  * Making it more suitable for the spring model.
+ * This should initialize and perform calculation a bit faster, and also
+ * use a bit less memory
  */
 
 export default function(links) {
@@ -26,8 +28,8 @@ export default function(links) {
         // jiggle so it wont divide / multiply by zero after this
         source = link.source;
         target = link.target;
-        x = target.x - source.x || jiggle();
-        y = target.y - source.y || jiggle();
+        x = target.x + target.vx - source.x - source.vx || jiggle();
+        y = target.y + target.vy - source.y - source.vy || jiggle();
         l = Math.sqrt(x * x + y * y);
         l = (l - distances[i]) / l  * dataSizeFactor;
         x *= l, y *= l;
@@ -41,13 +43,11 @@ export default function(links) {
 
   function initialize() {
     if (!nodes) return;
-    console.log("CUSTOM LINK FORCE");
     dataSizeFactor = 0.5/(nodes.length-1);
     initializeDistance();
   }
 
   function initializeDistance() {
-    console.log("INIT DISTANCE", links.length);
     if (!nodes) return;
 
     for (var i = 0, n = links.length; i < n; ++i) {