fix upgradeReq is undefined

This address bug joeferner#149 (maybe it even fixes it - a review would be nice here "works on my machine" ;)

Author: acklenx

lib/proxy.js

@@ -68,7 +68,10 @@ Proxy.prototype.listen = function(options, callback) {
     self.httpServer.on('request', self._onHttpServerRequest.bind(self, false));
     self.wsServer = new WebSocket.Server({ server: self.httpServer });
     self.wsServer.on('error', self._onError.bind(self, 'HTTP_SERVER_ERROR', null));
-    self.wsServer.on('connection', self._onWebSocketServerConnect.bind(self, false));
+    self.wsServer.on('connection', (ws, req) => {
+		  ws.upgradeReq = req;
+		  self._onWebSocketServerConnect.bind(self, false);
+	  });
     const listenOptions = {
       host: self.httpHost,
       port: self.httpPort