Get rid of all the library tags.

lib/src/barback/dependency_computer.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.
 
-library pub.barback.dependency_computer;
-
 import 'package:barback/barback.dart';
 import 'package:path/path.dart' as p;
 
 import '../dart.dart';
 import '../io.dart';
 import '../package.dart';
 import '../package_graph.dart';
 import '../pubspec.dart';
 import '../utils.dart';
 import 'cycle_exception.dart';
@@ skipping 437 matching lines @@
       return null;
     }
 
     _directives[libraryUri] =
         parseImportsAndExports(readTextFile(library), name: library)
         .map((directive) => Uri.parse(directive.uri.stringValue))
         .toSet();
     return _directives[libraryUri];
   }
 }