Refactor DateTime Holidays Collection

[leviferreira]

On the holiday collection, now we use strings to compare if a date is a holiday, we should implement a DateTime collection instance to set the holidays and compare objects not strings. I think we should do that in the new method "isBetween".

What do you think about it @marcelsud ?

From:

    /**
    * Set Holidays
    * @param array $holidays 
    */
    public function setHolidays($holidays)
    {
        $this->holidays = $holidays;
    }

To:

    /**
    * Set Holidays
    * @param DateTimeCollection $holidays 
    */
    public function setHolidays(DateTimeCollection $holidays)
    {
        $this->holidays = $holidays;
    }

Or we could use a Dependency Injection on the DateTime Class

     /**
     * Construct Method
     * @param string $time
     * @param DateTimeZone $timezone
     * @param DateTimeCollection $holidays
     */
    public function __construct(string $time, DateTimeZone $timezone = null, DateTimeCollection $holidays = null)
    {
         parent::__construct($time, $timezone);
         $this->holidays = $holidays;
    }