Allow .js at the end of module names

Issue google#1221

Author: arv

src/runtime/TraceurLoader.js

@@ -63,9 +63,10 @@ export class TraceurLoader extends Loader {
     load.metadata.traceurOptions = load.metadata.traceurOptions || {};
     var options = load.metadata.traceurOptions;
     var asJS;
-    if (options && options.script) {
+    if (/\.js$/.test(normalizedModuleName) || options && options.script) {
       asJS = normalizedModuleName;
     } else {
+      // Backwards compat.
       asJS = normalizedModuleName + '.js';
     }
 

test/unit/runtime/Loader.js

@@ -65,7 +65,9 @@ suite('Loader.js', function() {
     load.normalizedName = 'abc/def';
     assert.equal(loader.locate(load), 'http://example.org/a/abc/def.js');
     load.normalizedName = 'abc/def.js';
-    assert.notEqual(loader.locate(load), 'http://example.org/a/abc/def.js');
+    assert.equal(loader.locate(load), 'http://example.org/a/abc/def.js');
+    load.normalizedName = './abc/def.js';
+    assert.equal(loader.locate(load), 'http://example.org/a/abc/def.js');
   });
 
   test('traceur@', function() {