fix(animation): temporary fix for Animation symbol conflict

PR 808 will address this.

Author: chirayuk

test/_specs.dart

@@ -1,14 +1,14 @@
 library ng_specs;
 
-import 'dart:html';
+import 'dart:html' hide Animation;
 import 'package:unittest/unittest.dart' as unit;
 import 'package:angular/angular.dart';
 import 'package:angular/mock/module.dart';
 import 'package:collection/wrappers.dart' show DelegatingList;
 
 import 'jasmine_syntax.dart' as jasmine_syntax;
 
-export 'dart:html';
+export 'dart:html' hide Animation;
 export 'package:unittest/unittest.dart';
 export 'package:unittest/mock.dart';
 export 'package:di/dynamic_injector.dart';