title: grunt-contrib-copy - ignore folder when copying
body: <p>Given the following source tree:</p>
  
  <pre><code>dev
   丨- psd
       丨- psd.psd
       丨- png.png
   丨- css
       丨- css.css
   丨- image
       丨- 1.jpg
       丨- 2.png
   丨html.html
  </code></pre>
  
  <p>How do I copy to the pub directory ignoring the psd folder as seen below?</p>
  
  <pre><code>pub
   丨- css
       丨- css.css
   丨- image
       丨- 1.jpg
       丨- 2.png
   丨html.html
  </code></pre>
  
  <p>I tried the following:</p>
  
  <pre><code>{
   expand: true,
   src: ['dev/**/*', '!dev/psd/**/*'],
   dest: 'pub/'
  }
  </code></pre>
  
  <p>But this results in an empty <code>psd</code> directory</p>