Fix lint warnings

gatsby-config.js

@@ -6,8 +6,6 @@
 
 'use strict';
 
-const {join} = require('path');
-
 module.exports = {
   siteMetadata: {
     title: 'React: A JavaScript library for building user interfaces',

gatsby-node.js

@@ -6,8 +6,6 @@
 
 'use strict';
 
-const recursiveReaddir = require('recursive-readdir');
-const {readFileSync} = require('fs');
 const {resolve} = require('path');
 const webpack = require('webpack');
 

src/templates/codepen-example.js

@@ -4,11 +4,6 @@ import React, {Component} from 'react';
 import Container from 'components/Container';
 import {colors} from 'theme';
 
-const EXTERNALS = [
-  'https://unpkg.com/react/umd/react.development.js',
-  'https://unpkg.com/react-dom/umd/react-dom.development.js',
-];
-
 // Copied over styles from ButtonLink for the submit btn
 const primaryStyle = {
   backgroundColor: colors.brand,