refactor(tests): exctract createElement into a helper

modules/test_lib/src/test_lib.dart

@@ -6,6 +6,7 @@ import 'package:unittest/unittest.dart' hide expect;
 import 'dart:mirrors';
 import 'dart:async';
 import 'package:reflection/reflection.dart';
+import 'package:facade/dom.dart';
 import 'package:reflection/reflection_capabilities.dart';
 
 bool IS_DARTIUM = true;
@@ -67,4 +68,8 @@ _handleAsync(fn) {
   }
 
   return fn;
+}
+
+el(String html) {
+  return DOM.createTemplate(html).content.firstChild;
 }

modules/test_lib/src/test_lib.es6

@@ -1,3 +1,5 @@
+import {DOM} from 'facade/dom';
+
 export var describe = window.describe;
 export var xdescribe = window.xdescribe;
 export var ddescribe = window.ddescribe;
@@ -127,4 +129,9 @@ function mapToString(m) {
     res.push(`${k}:${v}`);
   });
   return `{ ${res.join(',')} }`;
+}
+
+
+export function el(html) {
+  return DOM.createTemplate(html).content.firstChild;
 }