update elements and fix some bugs

test/paper_slider_test.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 @TestOn('browser')
 library polymer_elements.test.paper_slider_test;
 
 import 'package:polymer_elements/paper_input.dart';
 import 'package:polymer_elements/paper_slider.dart';
 import 'package:polymer_interop/polymer_interop.dart';
 import 'package:test/test.dart';
@@ skipping 88 matching lines @@
     });
 
     test('editable', () async {
       slider.min = 0;
       slider.max = 10;
       slider.step = 1;
       slider.editable = true;
 
       await wait(1);
       slider.value = 2;
-      expect((slider.$$('#input') as PaperInput).value, '${slider.value}');
+      expect((slider.$$('#input') as PaperInput).value, slider.value);
     });
 
     test('decimal values', () async {
       slider.min = 0;
       slider.max = 1;
       slider.value = slider.min;
       slider.step = 0.1;
 
       slider.increment();
 
@@ skipping 46 matching lines @@
           100;
 
       slider.min = 0;
       slider.max = 100;
       down(slider.$['sliderBar'], cursor);
 
       return done;
     });
   });
 }