Link, remove links parameter

src/link.js

@@ -8,15 +8,13 @@ import jiggle from "./jiggle";
  * - removed other unused functions
  * Alpha should be constant 1 for accurate simulation
  */
-export default function(links) {
+export default function() {
   var dataSizeFactor,
       distance = constant(30),
       distances = [],
       nodes,
       iterations = 1;
 
-  if (links == null) links = [];
-
   function force(alpha) {
     // Each iteration in a tick
     for (var k = 0, n = nodes.length, source, target, i, j, x, y, l; k < iterations; ++k) {