Fix #254 use https module for xhr requests within node if needed

Author: brycekahle

lib/transport/driver/xhr.js

@@ -3,6 +3,7 @@
 var EventEmitter = require('events').EventEmitter
   , inherits = require('inherits')
   , http = require('http')
+  , https = require('https')
   , URL = require('url-parse')
   ;
 
@@ -26,7 +27,8 @@ function XhrDriver(method, url, payload, opts) {
   , agent: false
   };
 
-  this.req = http.request(options, function(res) {
+  var protocol = parsedUrl.protocol === 'https:' ? https : http;
+  this.req = protocol.request(options, function(res) {
     res.setEncoding('utf8');
     var responseText = '';