title: What is '$:.unshift File.dirname(__FILE__)' doing?
body: <p>What is the following doing, and why is it at the top of the page?</p>
  
  <pre><code>$:.unshift File.dirname(__FILE__)
  </code></pre>
  
  <p><a href="https://github.com/mojombo/jekyll/blob/master/lib/jekyll.rb" rel="noreferrer">https://github.com/mojombo/jekyll/blob/master/lib/jekyll.rb</a></p>