Added: holidays and custom classes by date

Added holiday_dates property to set a custom class (dp_holiday and dp_holiday_disabled) for certain holidays. Uses the same date format as disable_dates and enable_dates. If holiday and weekend fall on the same day, the dp_holiday class is preferred and dp_weekend is not used.
Example:
$("#date").Zebra_DatePicker({
	holiday_dates: [
		'* * * 0', // Every Sunday is a holiday
		'20 08 2014', // August 20, 2014 is a holiday
		'24 02 *', // February 24 is a holiday every year
	]
});

Added class_by_dates property to set additional custom classes for certain dates. Contains key-array pairs where keys represent the custom class, and arrays use the same format as disable_dates and enable_dates.
Example:
$("#date").Zebra_DatePicker({
class_by_dates: {
	'testclass':[
		'* * * 1', // every Monday gets class "testclass"; if disabled, then "testclass_disabled"
		'11 07 2014' // July 11, 2014 gets class "testclass"
	],
	'testclass2':[
		'* * * 2', // every Tuesday gets class "testclass2"
		'12 07 2014' // July 12, 2014 gets class "testclass"
	],
}
});