modify the minDate and maxDate values

[Ali-Khakshoor]

#248 In the minDate/maxDate example section, you mistakenly provided the value "UTC in seconds".

http://babakhani.github.io/PersianWebToolkit/doc/datepicker/example/#mindate The unix() method returns the UTC time in seconds.

However, the values minDate and maxDate should be entered as "UTC milliseconds" to work correctly (not in seconds). If entered in seconds, the minimum selectable date will be approximately 50 years before the expected date.

The code snippet below demonstrates the difference. Please check this jsFiddle: https://jsfiddle.net/Khakshoor/yjpk93aw/2/