title: Stripe gem is not working for create_reversal method
body: <p>I am using <a href="https://github.com/stripe/stripe-ruby" rel="nofollow noreferrer">ruby gem</a> for stripe integration. I am able to create transfer from this gem but when I try to use <code>create_reversal</code>.</p>
  <pre><code>Stripe::Transfer.create_reversal('Xxxxxxxxx')
  </code></pre>
  <p>when I use this method I am getting an error like</p>
  <blockquote>
  <p>NoMethodError: undefined method `create_reversal' for
  Stripe::Transfer:Class</p>
  </blockquote>
  <p>Any suggestion will be appreciated!</p>