fix fs

index.js

 const browserify = require("browserify");
 const Uglify = require("uglify-js");
+const fs = require("fs");
 
 function bundle(input_path, output_path, options = {}) {
     if (options.minify) {

package.json

 {
   "name": "simple-browser-js-bundler",
-  "version": "0.1.0",
+  "version": "0.1.1",
   "description": "An excessively simple javascript bundler based and browserify and uglify-js",
   "main": "index.js",
   "scripts": {