Add markdown to third_party/pkg

tools/list_pkg_directories.py

 #!/usr/bin/env python
 # 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.
 
 '''Tool for listing the directories under pkg, with their lib directories.
 Used in pkg.gyp. Lists all of the directories in the current directory

[Bob Nystrom, 2013/07/08 16:40:08]

Update this since now it doesn't look in the current directory.

[Emily Fortuna, 2013/07/08 17:36:30]

Done. Looks like this was already a bit out of date since the usage was wrong. 

 which have a lib subdirectory.
 
 Usage:
   python tools/list_pkg_directories.py
 '''
 
 import os
 import sys
 
 def main(argv):
-  paths = map(lambda x: x + '/lib', filter(os.path.isdir, os.listdir(argv[1])))
-  for lib in filter(lambda x: os.path.exists(x), paths):
-    print lib
+  paths = map(lambda x: x + '/lib', filter(lambda x: os.path.isdir(
+      os.path.join(argv[1], x)), os.listdir(argv[1])))

[Bob Nystrom, 2013/07/08 16:40:08]

Make a variable for argv[1] so it's clear what it's for.

[Emily Fortuna, 2013/07/08 17:36:30]

Done.

+  for lib in filter(lambda x: os.path.exists(os.path.join(argv[1], x)), paths):
+    print os.path.join(argv[1], lib)
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))