title: Laravel validator `required` fails for empty string also
body: <p>I'm trying laravel <code>required</code> validator in my code, unfortunately it fails for even empty string. I do not want it fail for empty string. </p>
  
  <pre><code>$validator = \Validator::make(array("name"=&gt;""), array("name"=&gt;"required"));
  if ($validator-&gt;fails()){
      var_dump($validator-&gt;messages());
  } else {
      die("no errors :)");
  }
  </code></pre>
  
  <p>It gives me the following output</p>
  
  <pre><code>object(Illuminate\Support\MessageBag)[602]
    protected 'messages' =&gt; 
      array (size=1)
        'name' =&gt; 
          array (size=1)
            0 =&gt; string 'The name field is required.' (length=27)
    protected 'format' =&gt; string ':message' (length=8)
  </code></pre>
  
  <p>It is supposed to pass, since i'm giving an empty string as the <code>name</code> field. </p>
  
  <p>The above behavior happens in OSX environment (PHP Version 5.5.18), but it works fine in linux environment (PHP Version 5.5.9-1ubuntu4.5).</p>