title: ReferenceError: process is not defined when requiring Shelljs in ReactJS
body: <p>I am trying to require shelljs in my core React component.</p>
  
  <pre><code>import React, { Component } from 'react';
  import {render} from 'react-dom';
  import Header from './components/Header';
  
  const shell = require('shelljs');
  
  class App extends Component {
      render() {
          console.log("First component mounting");
          console.log("First component mounting");
          return (
              &lt;Header /&gt;
          )
      }
  }
  
  render(&lt;App /&gt;, document.getElementById('root'));
  </code></pre>
  
  <p>When I run</p>
  
  <pre><code>webpack build
  </code></pre>
  
  <p>I get no errors, then I run my server and I get the following console error.</p>
  
  <p>I'm using jekyll as my server side. Currently transitioning from the normal jekyll implementation to React only.
  React is well implemented cause i tested the Header component before importing the shelljs module</p>
  
  <pre><code>ReferenceError: process is not defined
  </code></pre>
  
  <p>I'm new to using modules in javascript, thanks in advance.</p>