fix: url in test

Author: Yoseph Maguire

examples/wss/client_with_proxy.js

@@ -1,6 +1,7 @@
 'use strict'
 
 var mqtt = require('mqtt')
+var url = require('url')
 var HttpsProxyAgent = require('https-proxy-agent')
 /*
 host: host of the endpoint you want to connect e.g. my.mqqt.host.com