element-ui的日期选择器，某日之前不可选，某日之后不可选

pickerOptionLater是在data的return里面定义的。

pickerOptionLater: {

    disabledDate(time) {

        var date = new Date('2018-06-30 24:00:00:000')

        var thatDay = date.getTime()

        return time.getTime() < thatDay

    }

}