title: How to include subdirectories in gulp task
body: <p>I am just getting started with Gulp.</p>
  
  <p>I have this:</p>
  
  <pre><code>var path = require('path');
  var appRoot = 'src/';
  var outputRoot = 'dist/';
  
  module.exports = {
  root: appRoot,
  source: appRoot + '**/*.js',
  html: appRoot + '**/*.html',
  style: 'styles/**/*.css',
  output: outputRoot,
  doc:'./doc',
  e2eSpecsSrc: 'test/e2e/src/*.js',
  e2eSpecsDist: 'test/e2e/dist/'
  </code></pre>
  
  <p>};</p>
  
  <p>This pathing is used to convert the source files from ES6 to ES5, and then drop in them in the dist directory.  This all works fine.</p>
  
  <p>However, it only takes the files from the src directory, not subfolders.  How do I include the subfolders such as src\dir1 and src\dir2?</p>