title: Test if value is an integer in Sass
body: <p>How can I test whether a value is an integer in Sass?</p>
  
  <p>I saw some documentation stating there was an <code>int?</code> function but I don't think I'm using it correctly. That, or I have misunderstood the documentation.</p>
  
  <p>I am currently doing this, but am getting an error:</p>
  
  <pre><code>int?(16)
  </code></pre>