py23: alias itertools.izip as 'zip'

so we consistently use python3 zip iterator on both py2 and py3

Lib/fontTools/misc/py23.py

@@ -250,7 +250,7 @@ def open(file, mode='r', buffering=-1, encoding=None, errors=None,
 			file, mode, buffering, encoding, errors, newline, closefd)
 
 
-# always use iterator for 'range' on both py 2 and 3
+# always use iterator for 'range' and 'zip' on both py 2 and 3
 try:
 	range = xrange
 except NameError:
@@ -259,6 +259,11 @@ except NameError:
 def xrange(*args, **kwargs):
 	raise Py23Error("'xrange' is not defined. Use 'range' instead.")
 
+try:
+	from itertools import izip as zip
+except ImportError:
+	zip = zip
+
 
 import math as _math