Node version (or tell us if you're using electron or some other framework):

Node - v4.5.0
NPM - 2.15.9

ShellJS version (the most recent version/Github branch you see the bug on):

^0.7.4

Operating system:

Mac OSX El Capitan

Description of the bug:

I have a post install script that requires shelljs - I cloned the repository and then run npm install. The script fails when I require shelljs with an issue about node's global fs. When I remove the require to shelljs, it does not throw an error.

Example ShellJS command to reproduce the error:

#! /usr/bin/env node

/*jshint esversion: 6, node: true */
"use strict";

const shell = require("shelljs");

    throw err;
    ^

Error: Cannot find module 'fs.realpath'
    at Function.Module._resolveFilename (module.js:325:15)
    at Function.Module._load (module.js:276:25)
    at Module.require (module.js:353:17)
    at require (internal/module.js:12:17)`