title: Converting integers into words and roman numerals
body: <p>Is there a library to convert integers into strings, so that they (integers) will be represented as words? For example:</p>
  
  <blockquote>
    <p>21 => "twenty one"</p>
  </blockquote>
  
  <p>I'm also interested in converting integers into strings that represent them as Roman numerals:</p>
  
  <blockquote>
    <p>21 => "XXI"</p>
  </blockquote>
  
  <p>It's not a problem for me to write such converting functions, but I don't want to reinvent the wheel.</p>