Get rid of all the library tags.

lib/src/barback/transformer_id.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 pub.barback.transformer_id;
-
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 import 'package:source_span/source_span.dart';
 
 import '../utils.dart';
 
 /// A list of the names of all built-in transformers that pub exposes.
 const _BUILT_IN_TRANSFORMERS = const ['\$dart2js'];
 
@@ skipping 69 matching lines @@
     if (path != null) {
       return new Future.value(new AssetId(package, 'lib/$path.dart'));
     }
 
     var transformerAsset = new AssetId(package, 'lib/transformer.dart');
     return barback.getAssetById(transformerAsset).then((_) => transformerAsset)
         .catchError((e) => new AssetId(package, 'lib/$package.dart'),
             test: (e) => e is AssetNotFoundException);
   }
 }