[minor] Add missing space

lib/node-http-proxy.js

@@ -192,7 +192,7 @@ exports.createServer = function () {
   if (!callback) {
     // WebSocket support: if callback is empty tunnel 
     // websocket request automatically
-    server.on('upgrade', function(req, socket, head) {
+    server.on('upgrade', function (req, socket, head) {
       // Tunnel websocket requests too
       
       proxy.proxyWebSocketRequest(req, socket, head, {