fixed gulp build

lib/abi.js

@@ -46,7 +46,7 @@ var findMethodIndex = function (json, methodName) {
 };
 
 var padLeft = function (string, chars) {
-    return Array(chars - string.length + 1).join("0") + string;
+    return new Array(chars - string.length + 1).join("0") + string;
 };
 
 var setupInputTypes = function () {