title: Error when using composer require-dev.mikey179/vfsStream is invalid
body: <p>I am using Amazon LightSail and the CodeIgniter framework. Trying to install PhpSpreadsheet - <a href="https://phpspreadsheet.readthedocs.io/en/latest/#installation" rel="nofollow noreferrer">https://phpspreadsheet.readthedocs.io/en/latest/#installation</a> using</p>
  <pre><code>composer require phpoffice/phpspreadsheet
  </code></pre>
  <p>However I then am greeted with</p>
  <pre><code> [RuntimeException]
    require-dev.mikey179/vfsStream is invalid, it should not contain uppercase characters. Please use mikey179/vfsstream instead.
  </code></pre>
  <p>I did the usual Googling but couldn't find anything specific.</p>
  <p>When I run</p>
  <pre><code>composer.phar show
  </code></pre>
  <p>I get the error from above.</p>