title: Finding versions of Python that are available for "pyenv install"
body: <p>I want to know what Python versions I could install using the <code>pyenv install</code> command.  <code>pyenv versions</code> lists only installed versions and does not appear to have an option to list available versions.</p>
  
  <p><strong>How can I find out what versions of Python I can install with <code>pyenv install</code>?</strong></p>