Merge pull request #140 from X9VoiD/bump-version

Add OTD version 0.6.4.0

Author: X9VoiD

site/_data/otd-versions.json

@@ -17,5 +17,6 @@
   "0.6.1.0",
   "0.6.1.1",
   "0.6.2.0",
-  "0.6.3.0"
+  "0.6.3.0",
+  "0.6.4.0"
 ]