Get rid of all the library tags.

lib/src/barback.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;
-
 import 'package:barback/barback.dart';
 import 'package:path/path.dart' as p;
 import 'package:pub_semver/pub_semver.dart';
 
 /// The currently supported versions of packages that this version of pub works
 /// with.
 ///
 /// Pub implicitly constrains these packages to these versions as long as
 /// barback is a dependency.
 ///
@@ skipping 63 matching lines @@
   if (parts.length <= index + 1) {
     throw new FormatException(
         'Invalid URL path "${url.path}". Expected package name '
         'after "packages".');
   }
 
   var package = parts[index + 1];
   var assetPath = p.url.join("lib", p.url.joinAll(parts.skip(index + 2)));
   return new AssetId(package, assetPath);
 }