removed promise dependency, updated readme, fixed node.js version of lib

lib/httpsync.js

@@ -21,6 +21,10 @@
  * @date 2014
  */
 
+if (process.env.NODE_ENV !== 'build') {
+        var XMLHttpRequest = require('xmlhttprequest').XMLHttpRequest; // jshint ignore:line
+}
+
 var HttpSyncProvider = function (host) {
     this.handlers = [];
     this.host = host || 'http://localhost:8080';