move delete_file and remove_sourcemap_comment transformers to code_transformers

pkg/code_transformers/lib/src/delete_file.dart

Index: pkg/code_transformers/lib/src/delete_file.dart
diff --git a/pkg/polymer/lib/src/build/delete_file.dart b/pkg/code_transformers/lib/src/delete_file.dart
similarity index 94%
copy from pkg/polymer/lib/src/build/delete_file.dart
copy to pkg/code_transformers/lib/src/delete_file.dart
index b417605ee84e25dd33c3e3481c458c628f5bdd30..147e3463d8df8e0307f0faf09f644196a389a39d 100644
--- a/pkg/polymer/lib/src/build/delete_file.dart
+++ b/pkg/code_transformers/lib/src/delete_file.dart
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /// Transformer that deletes everything that it sees, but only in release mode.
-library web_components.src.delete_file;
+library code_transformers.src.delete_file;
 
 import 'dart:async';
 import 'package:barback/barback.dart';