Improve code quality and write tests

node_modules/object-keys/isArguments.js

@@ -0,0 +1,17 @@
+'use strict';
+
+var toStr = Object.prototype.toString;
+
+module.exports = function isArguments(value) {
+	var str = toStr.call(value);
+	var isArgs = str === '[object Arguments]';
+	if (!isArgs) {
+		isArgs = str !== '[object Array]' &&
+			value !== null &&
+			typeof value === 'object' &&
+			typeof value.length === 'number' &&
+			value.length >= 0 &&
+			toStr.call(value.callee) === '[object Function]';
+	}
+	return isArgs;
+};