use the system copy of six

--- a/boto/compat.py
+++ b/boto/compat.py
@@ -46,16 +46,16 @@ except (AttributeError, ImportError):
     # This is probably running on App Engine.
     expanduser = (lambda x: x)
 
-from boto.vendored import six
+import six
 
-from boto.vendored.six import BytesIO, StringIO
-from boto.vendored.six.moves import filter, http_client, map, _thread, \
+from six import BytesIO, StringIO
+from six.moves import filter, http_client, map, _thread, \
                                     urllib, zip
-from boto.vendored.six.moves.queue import Queue
-from boto.vendored.six.moves.urllib.parse import parse_qs, quote, unquote, \
+from six.moves.queue import Queue
+from six.moves.urllib.parse import parse_qs, quote, unquote, \
                                                  urlparse, urlsplit
-from boto.vendored.six.moves.urllib.parse import unquote_plus
-from boto.vendored.six.moves.urllib.request import urlopen
+from six.moves.urllib.parse import unquote_plus
+from six.moves.urllib.request import urlopen
 
 if six.PY3:
     # StandardError was removed, so use the base exception type instead