Pass field element reference into validation callback

[velosipedist]

I have custom validators which not just check some hardcoded data conditions, but depends on validated input and/or it's neighbours state.

It requires at least reference to the input itself.

At first glance, it can be solved just adding input reference here (passing it through then into validateThroughValidator()).

[efreibe]

I've resolved it using this code:

validateThroughValidator: function (value, constraints, priority) {
      var that = this;
      $.each(constraints, function() { this.$element = that.$element });
      return window.ParsleyValidator.validate.apply(window.ParsleyValidator, [value, constraints, priority]);
    },

[marcandre]

Related to #839

[chibicode]

This would be very useful :+1: