title: bundle update puma won't work
body: <p>I tried using <code>bundle update puma</code>but I get a <code>Could not locate Gemfile</code> error. I'm in the same directory as the gemfile. My <code>dir</code> has</p>
  
  <pre><code>26/02/2017  12:39 AM               490 puma
  26/02/2017  12:39 AM               234 puma.bat
  26/02/2017  12:39 AM               493 pumactl
  26/02/2017  12:39 AM               237 pumactl.bat
  </code></pre>