Remove unused import in polymer, fix comment.

pkg/polymer/lib/polymer.dart

 // Copyright (c) 2012, 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.
 
 /// Custom HTML tags, data binding, and templates for building
 /// structured, encapsulated, client-side web apps.
 ///
 /// Polymer.dart, the next evolution of Web UI,
 /// is an in-progress Dart port of the
 /// [Polymer project](http://www.polymer-project.org/).
@@ skipping 51 matching lines @@
 // bots.
 @MirrorsUsed(metaTargets:
     const [Reflectable, ObservableProperty, PublishedProperty, CustomTag,
         ObserveProperty],
     targets: const [PublishedProperty, ObserveProperty],
     override: const ['smoke.mirrors'])
 import 'dart:mirrors' show MirrorsUsed;    // ** see important note above
 
 import 'package:logging/logging.dart' show Logger, Level;
 import 'package:observe/observe.dart';
-import 'package:path/path.dart' as path;
 import 'package:polymer_expressions/polymer_expressions.dart'
     show PolymerExpressions;
 import 'package:smoke/smoke.dart' as smoke;
 import 'package:template_binding/template_binding.dart';
 
 import 'deserialize.dart' as deserialize;
 
 export 'package:observe/observe.dart';
 export 'package:observe/html.dart';
 
 part 'src/declaration.dart';
 part 'src/instance.dart';
 part 'src/job.dart';
 part 'src/loader.dart';