Add a copy of argparse 1.2.1 to chromite's third_party.

Adding a copy of argparse from the Python Libraries to chromite.third_party.
I've also added a README/LICENSE for chromite.third_party

BUG=None
TEST=Tested import on Lucid. Got version based on easy_install on older
Lucid machine.

Change-Id: I12e5f59a7997b633f6688e15e348e3abb7e77d96
Reviewed-on: https://gerrit.chromium.org/gerrit/35314
Commit-Ready: Chris Sosa <sosa@chromium.org>
Reviewed-by: Chris Sosa <sosa@chromium.org>
Tested-by: Chris Sosa <sosa@chromium.org>
diff --git a/scripts/cros.py b/scripts/cros.py
index 10eca53..8bf02e3 100644
--- a/scripts/cros.py
+++ b/scripts/cros.py
@@ -4,12 +4,11 @@
 
 import sys
 
-# Older version of Python might be missing argparse.
+# Older versions of Python might be missing argparse.
 try:
   import argparse
 except ImportError:
-  print >> sys.stderr, "argparse missing. sudo apt-get install python-argparse"
-  sys.exit(1)
+  from chromite.third_party import argparse
 
 from chromite.cros import commands