Remove barback from the repo.

pkg/barback/example/lazy_transformer/lib/transformer.dart

-// Copyright (c) 2014, 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.
-
-import 'package:barback/barback.dart';
-
-import 'dart:async';
-
-class CodedMessageConverter extends Transformer 
-                            implements LazyTransformer {
-
-  // A constructor named "asPlugin" is required. It can be empty, but
-  // it must be present.
-  CodedMessageConverter.asPlugin();
-
-  Future<bool> isPrimary(AssetId id) {
-    return new Future.value(id.extension == '.txt');
-  }
-
-  Future declareOutputs(DeclaringTransform transform) {
-    return new Future.value(transform.primaryId.changeExtension('.shhhhh'));
-  }
-
-  Future apply(Transform transform) {
-    return transform.primaryInput.readAsString().then((content) {
-
-      // The output file is created with the '.shhhhh' extension.
-      var id = transform.primaryInput.id.changeExtension('.shhhhh');
-
-      StringBuffer newContent = new StringBuffer();
-      for (int i = 0; i < content.length; i++ ) {
-        newContent.write(rot13(content[i]));
-      }
-      transform.addOutput(new Asset.fromString(id, newContent.toString()));
-    });
-  }
-
-  rot13(var ch) {
-    var c = ch.codeUnitAt(0);
-    if      (c >= 'a'.codeUnitAt(0) && c <= 'm'.codeUnitAt(0)) c += 13;
-    else if (c >= 'A'.codeUnitAt(0) && c <= 'M'.codeUnitAt(0)) c += 13;
-    else if (c >= 'n'.codeUnitAt(0) && c <= 'z'.codeUnitAt(0)) c -= 13;
-    else if (c >= 'N'.codeUnitAt(0) && c <= 'Z'.codeUnitAt(0)) c -= 13;
-    return new String.fromCharCode(c);
-  }
-}