function classUpdateDisabled($tag, $el, options) {
        classUpdate($tag, options.disabledClass, $el.is(":disabled"));
    }
Set or remove the "disabled" class for disabled elements, based on
if the element is detected to be disabled.

@param {jQuery} $tag Our Uniform span/div
@param {jQuery} $el Original form element
@param {Object} options Uniform options for this element