[javascript] Add '.js' extension to relative module imports

This is apparently a recent change in the ES6 spec:
google/traceur-compiler#1221
google/traceur-compiler#1692

Author: peferron

biconnected_components/javascript/biconnected_components.js

@@ -1,4 +1,4 @@
-import {AdjacencyList} from './adjacency_list';
+import {AdjacencyList} from './adjacency_list.js';
 
 export function articulations(graph) {
     if (graph.directed) {

biconnected_components/javascript/biconnected_components_test.js

@@ -1,6 +1,6 @@
 const assert = require('assert');
 
-import {articulations} from './biconnected_components';
+import {articulations} from './biconnected_components.js';
 
 const tests = [
     {

connected_components/javascript/connected_components.js

@@ -1,4 +1,4 @@
-import {AdjacencyList} from './adjacency_list';
+import {AdjacencyList} from './adjacency_list.js';
 
 export function connectedComponents(graph) {
     if (graph.directed) {

connected_components/javascript/connected_components_test.js

@@ -1,6 +1,6 @@
 const assert = require('assert');
 
-import {connectedComponents} from './connected_components';
+import {connectedComponents} from './connected_components.js';
 
 const tests = [
     {