title: Every nth element in a jQuery set
body: <p>I wanna select every nth in a jQuery set of elements.</p>
  
  <p>Eg.</p>
  
  <pre><code>&lt;ul&gt;
    &lt;li&gt;A&lt;/li&gt;
    &lt;li&gt;B&lt;/li&gt;
    &lt;li&gt;C&lt;/li&gt;
    &lt;li&gt;D&lt;/li&gt;
    &lt;li&gt;E&lt;/li&gt;
    &lt;li&gt;F&lt;/li&gt;
    &lt;li&gt;G&lt;/li&gt;
  &lt;/ul&gt;
  </code></pre>
  
  <ol>
  <li>How do I select every third (C and F) element?</li>
  <li>How do I select all other elements that is not every third (A, B, D, E, G) of the same set?</li>
  </ol>