added unit testing, and started implementing unit tests...phew

node_modules/async/internal/once.js

@@ -0,0 +1,15 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+    value: true
+});
+exports.default = once;
+function once(fn) {
+    return function () {
+        if (fn === null) return;
+        var callFn = fn;
+        fn = null;
+        callFn.apply(this, arguments);
+    };
+}
+module.exports = exports["default"];