code: function save() {
        var defer = new Defer
          , xhr = backbone.Model.prototype.save.apply(this, arguments);
  
        if (xhr) return xhr;
        defer.next(new Error('Could not validate model'));
  
        return defer;
      }
docs: Overrule the default save. Normally `save` returns `false` when validation
  fails. However this does not match the Node.JS callback pattern.
  
  @return {Defer} Promise XHR object
  @api public