Date validation added

I have added the following validators for dates:

* formattedDate: accepts a date is a given format (dd/mm/yyyy, mm/dd/yy etc) and validates a date string to ensure it matches the format.
* futureDate: determines if a given date is in the future.
* historicDate: determines if a given date is in the past.

I have also added unit tests for each of the above.