title: Require a lib directory in irb console
body: <p>Is there a way how to <code>require</code> all files in <code>lib</code> directory at once in <code>irb</code> console?: </p>
  
  <pre><code>irb ( project root )
  require './lib/' # not working  
  </code></pre>
  
  <p>structure</p>
  
  <pre><code>.
  |
  --lib 
    |
    |-- one.rb
    |-- two.rb
    |-- tree.rb
  </code></pre>
  
  <p><strong>EDIT</strong></p>
  
  <p>I prefer a solution where I can <code>require</code> files only once, not each time when I start <code>irb</code> session. </p>