Fix import error for itertools.izip on python 3.

Author: amotzg

mockredis/script.py

@@ -1,6 +1,11 @@
 import sys
 import threading
-from itertools import izip
+try:
+    # Python 2
+    from itertools import izip
+except ImportError:
+    # Python 3
+    izip = zip
 from mockredis.exceptions import ResponseError
 
 LuaLock = threading.Lock()