use fast implementations of tweetnacl serverside

lib/client/index.js

@@ -4,7 +4,7 @@ var nThen = require("nthen");
 
 var Util = require("../../www/common/common-util");
 
-var Nacl = require("tweetnacl");
+var Nacl = require("tweetnacl/nacl-fast");
 
 var Client = module.exports;