title: Require specific gem version in SASS & Compass
body: <p>I know this is probably more a Ruby question but I work on several projects where I've used compass plugins. Later on I upgrade these plugins and start new projects. The issue arises when I need to go back and make amends to an older project.</p>
  
  <p>How can I amend my config.rb file to use a specific version of a gem?</p>
  
  <p>For example I often use the Compass plugin:  <a href="http://rubygems.org/gems/html5-boilerplate/versions" rel="nofollow">http://rubygems.org/gems/html5-boilerplate/versions</a></p>
  
  <p>The line in my <code>config.rb</code> file looks like this:</p>
  
  <pre><code>require 'html5-boilerplate'
  </code></pre>
  
  <p>But I would need <code>1.0.0</code> for one project and <code>2.1.0</code> in another.</p>