fix: urlencode proxy username and password

Author: shirish87

index.js

@@ -98,7 +98,7 @@ var createBrowserStackClient = function (/* config.browserStack */config) {
   if (config.proxyHost && config.proxyPort) {
     config.proxyProtocol = config.proxyProtocol || 'http'
     var proxyAuth = (config.proxyUser && config.proxyPass)
-      ? (config.proxyUser + ':' + config.proxyPass + '@') : ''
+      ? (encodeURIComponent(config.proxyUser) + ':' + encodeURIComponent(config.proxyPass) + '@') : ''
     options.proxy = config.proxyProtocol + '://' + proxyAuth + config.proxyHost + ':' + config.proxyPort
   }