title: Laravel validation - input must be one of items in array
body: <p>Is there a built in validator in Laravel 5 that checks if value is in array of my whitelisted values sort of speak.. Something like:</p>
  
  <pre><code>$rules = [
      'field_name' =&gt; "required|in_array('yes', 'no', 'maybe')",
  ];
  </code></pre>