Let developer to change title and alt-title for custom drawing

[kambizzandi]

Hi Many thanks for this awesome component. I want to change title of main day and alt.day. But in your code (persian-datepicker.js v1.2.0) at line 3190 and 3191 this two variables are fixed and could not be changed by developer. I suggest this two lines changed for calling function with default behaviors and let developer to change this two functions.

current:

3190: title: calcedDate.format('D'),
3191: alterCalTitle: new persianDate(calcedDate.valueOf()).toCalendar(anotherCalendar[0]).toLocale(anotherCalendar[1]).format('D'),

new:

3190: title: this.getTitleForDraw(calcedDate),
3191: alterCalTitle: this.getAlterTitleForDraw(calcedDate, anotherCalendar),

and new functions:

...
    }, {
        key: 'getTitleForDraw',
        value: function getTitleForDraw(calcedDate) {
          return calcedDate.format('D');
        }
    }, {
        key: 'getAlterTitleForDraw',
        value: function getAlterTitleForDraw(calcedDate, anotherCalendar) {
          return new persianDate(calcedDate.valueOf()).toCalendar(anotherCalendar[0]).toLocale(anotherCalendar[1]).format('D');
        }
...

Thanks