title: How to run a specific version of a ruby gem
body: <p>I am running brakeman outside of my Gemfile, so am not using bundler.</p>
  
  <p>If I do <code>gem list</code>, I can see I have the following for brakeman</p>
  
  <pre><code>brakeman (3.3.3, 3.3.2, 3.1.4, 3.1.2)
  </code></pre>
  
  <p>But if I do <code>brakeman --version</code>, I get </p>
  
  <pre><code>brakeman 3.1.2
  </code></pre>
  
  <p>so I am not using the latest version.  If I do <code>gem update brakeman</code> or</p>
  
  <pre><code>gem update brakeman, '3.3.3,
  </code></pre>
  
  <p>I get</p>
  
  <pre><code>Updating installed gems
  Nothing to update
  </code></pre>
  
  <p>So how do I run brakeman  version 3.3.3?</p>