title: Susy: mixin applies, but throws error
body: <p>I just started to use Susy. When I apply span-columns() mixins, the markup does applies correctly, but sass throws an error: (Line 276: Undefined mixin 'span-columns'.)</p>
  
  <pre><code>#element-1 {
    @include span-columns(6, 12);
  }
  #element-2 {
    @include span-columns(6 omega, 12);
  }
  </code></pre>
  
  <ul>
  <li>Sass 3.3.0.alpha.3</li>
  <li>Compass 0.12.2</li>
  <li>susy-1.0.8</li>
  </ul>
  
  <p>-- Edit: Fixed - it was me assuming that including Susy in a previously included scss file would be suffice to work in the last included scss file (which in a way it did). I included Susy again.</p>