pkg/path: fixed tiny doc bug

pkg/path/lib/path.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.
 
 /// A comprehensive, cross-platform path manipulation library.
 ///
 /// ## Installing ##
 ///
 /// Use [pub][] to install this package. Add the following to your
 /// `pubspec.yaml` file.
@@ skipping 91 matching lines @@
 ///
 /// Trailing separators are ignored.
 ///
 ///     builder.basenameWithoutExtension('path/to/foo.dart/'); // -> 'foo'
 String basenameWithoutExtension(String path) =>
     _builder.basenameWithoutExtension(path);
 
 /// Gets the part of [path] before the last separator.
 ///
 ///     path.dirname('path/to/foo.dart'); // -> 'path/to'
-///     path.dirname('path/to');          // -> 'to'
+///     path.dirname('path/to');          // -> 'path'
 ///
 /// Trailing separators are ignored.
 ///
 ///     builder.dirname('path/to/'); // -> 'path'
 String dirname(String path) => _builder.dirname(path);
 
 /// Gets the file extension of [path]: the portion of [basename] from the last
 /// `.` to the end (including the `.` itself).
 ///
 ///     path.extension('path/to/foo.dart');    // -> '.dart'
@@ skipping 1008 matching lines @@
     // doesn't count.
     if (lastDot <= 0) return [file, ''];
 
     return [file.substring(0, lastDot), file.substring(lastDot)];
   }
 
   _ParsedPath clone() => new _ParsedPath(
       style, root, isRootRelative,
       new List.from(parts), new List.from(separators));
 }