title: LoadError: cannot load such file -- directory/file_name
body: <p>I have a file structure like</p>
  
  <pre><code>root
  |--lib
     |--root.rb
     |--extensions
        |--strings.rb
  </code></pre>
  
  <p>I want to be able to use methods in <code>string.rb</code> in <code>root.rb</code> file.</p>
  
  <p>So I added <code>require 'extensions/strings'</code> at the top of <code>root.rb</code> file.</p>
  
  <p>But I get <code>LoadError: cannot load such file -- extensions/strings.rb</code> error.</p>
  
  <p>How do I avoid this?</p>