Prepare release 0.6.4

Change-Id: I5f72c2fbf2a2ec86c108a47b4c854b069267276b
diff --git a/wscript b/wscript
index 3a90311..c5f8b33 100644
--- a/wscript
+++ b/wscript
@@ -26,7 +26,7 @@
 from waflib import Context, Logs, Utils
 import os, subprocess
 
-VERSION = '0.6.3'
+VERSION = '0.6.4'
 APPNAME = 'nfd'
 BUGREPORT = 'https://redmine.named-data.net/projects/nfd'
 URL = 'https://named-data.net/doc/NFD/'