add traceur test suite

test/fixtures/traceur/Classes/Skip_HTMLBlockquoteElement.js

@@ -0,0 +1,16 @@
+// Skip. Not implemented.
+// Only in browser.
+
+class CustomBlockquote extends HTMLBlockquoteElement {
+  constructor() {
+    this.custom = 42;
+  }
+}
+
+var customBlockquote = new CustomBlockquote;
+assert.equal(42, customBlockquote.custom);
+assert.equal('BLOCKQUOTE', customBlockquote.tagName);
+assert.isTrue(customBlockquote instanceof CustomBlockquote);
+assert.isTrue(customBlockquote instanceof HTMLBlockquoteElement);
+assert.isTrue(customBlockquote instanceof HTMLQuoteElement);
+assert.isTrue(customBlockquote instanceof HTMLElement);