title: Restangular error handling issue
body: <p>I'm having an issue with restangular. This code :     </p>
  
  <pre><code>Restangular.one("undefined_ressource").get().then(
      function(res){
          console.log("success", res.code);
      },
      function (res) {
          console.log("fail", res.code);
     }
  );
  </code></pre>
  
  <p>Tries to get the url <code>http://api.local.com/undefined_ressource</code> which does not exits. My server returns a 404, as expected, but the fail log is never fired. Intead it goes in the success callback and logs <code>"success 404"</code> to the console.</p>
  
  <pre><code>Angular version 1.2.15
  Restangular version 1.3.1
  </code></pre>
  
  <p>Any help would be welcomed! Thanks</p>