Updates examples using ES2015 class syntax

js/spec/gilded_rose_spec.js

@@ -1,8 +1,8 @@
 describe("Gilded Rose", function() {
 
   it("should foo", function() {
-    items = [ new Item("foo", 0, 0) ];
-    update_quality();
+    const gilgedRose = new Shop([ new Item("foo", 0, 0) ]);
+    const items = gilgedRose.updateQuality();
     expect(items[0].name).toEqual("fixme");
   });