Switch pkg packages, pub, and dartdoc to use package: imports.

utils/pub/package.dart

 // Copyright (c) 2012, 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 package;
 
 import 'dart:async';
 
-import '../../pkg/pathos/lib/path.dart' as path;
+import 'package:pathos/path.dart' as path;
 
 import 'io.dart';
 import 'pubspec.dart';
 import 'source.dart';
 import 'source_registry.dart';
 import 'version.dart';
 
 final _README_REGEXP = new RegExp(r"^README($|\.)", caseSensitive: false);
 
 /// A named, versioned, unit of code and resource reuse.
@@ skipping 187 matching lines @@
 
 class PubspecNameMismatchException implements Exception {
   final String expectedName;
   final String actualName;
 
   PubspecNameMismatchException(this.expectedName, this.actualName);
 
   String toString() => 'The name you specified for your dependency, '
     '"$expectedName", doesn\'t match the name "$actualName" in its pubspec.';
 }