Prepare release 0.6.4

Refs: #4916
Change-Id: I8aa91d5314016e7f9698e4ee457f5a8d22f3ad67
diff --git a/wscript b/wscript
index 3f41bcb..84038c9 100644
--- a/wscript
+++ b/wscript
@@ -1,6 +1,6 @@
 # -*- Mode: python; py-indent-offset: 4; indent-tabs-mode: nil; coding: utf-8; -*-
 
-VERSION = '0.6.2'
+VERSION = '0.6.4'
 APPNAME = 'ndn-tools'
 GIT_TAG_PREFIX = 'ndn-tools-'