code: function kind (date, compareTo) {
    date = this.toDatetime(date);
    compareTo = compareTo ? this.toDatetime(compareTo) : new Date();
    if (!date || !compareTo) {
      return '';
    }
    var diff =  (compareTo - date) / 1000;
    var surfix = 0 < diff ? '前' : '後';
    diff = Math.abs(diff);
  
    var i = POINTS.length - 1;
    var point;
    for(point = null;point = POINTS[i]; i--) {
      if (point[2] <= diff) {
        var x = parseInt(diff / point[0], 10) + (point[2] <= diff % point[0] ? 1 : 0);
        return x + point[1] + surfix;
      }
    }
    return 'たった今';
  }
docs: 人間が理解しやすい口語表記にする
  @method kind
  @param  {DATE}   date
  @param  {DATE}   compareTo
  @return {String}