move delete_file and remove_sourcemap_comment transformers to code_transformers

pkg/code_transformers/test/remove_sourcemap_comment_test.dart

 // Copyright (c) 2013, 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.
 
-library polymer.test.build.remove_sourcemap_comment_test;
+library code_transformers.test.remove_sourcemap_comment_test;
 
 import 'package:barback/barback.dart';
-import 'package:polymer/src/build/remove_sourcemap_comment.dart';
+import 'package:code_transformers/src/remove_sourcemap_comment.dart';
+import 'package:code_transformers/tests.dart';
 import 'package:unittest/compact_vm_config.dart';
 import 'package:unittest/unittest.dart';
-import 'common.dart';
 
 final phases = [[new RemoveSourcemapComment.asPlugin(
     new BarbackSettings({}, BarbackMode.RELEASE))]];
 
 void main() {
   useCompactVMConfiguration();
 
   testPhases('removes sourcemap comments', phases, {
       'a|web/test.js': '''
           var i = 0;
           //# sourceMappingURL=*.map''',
   }, {
       'a|web/test.js': '''
           var i = 0;''',
   });
 }