title: Laravel - find by custom column or fail
body: <p>There's <code>findOrFail()</code> method which throws 404 if nothing was found, e.g.:</p>
  
  <pre class="lang-php prettyprint-override"><code>User::findOrFail(1);
  </code></pre>
  
  <p>How can I find an entity by custom column or fail, something like this: </p>
  
  <pre class="lang-php prettyprint-override"><code>Page::findBySlugOrFail('about');
  </code></pre>