title: How to determine which ruby gem version is actually in use
body: <p>I'm doing some load testing with Unicorn on Heroku Celadon Cedar stack and I need to know which version of unicorn I used. I just included <code>gem 'unicorn'</code> in the <code>Gemfile</code>.  </p>
  
  <p>Is there anyway of knowing the unicorn version number?</p>
  
  <p><strong>EDIT</strong></p>
  
  <p>I'm using JRuby</p>