[TW-1808] adjust recurring tasks for holidays

_Eric Hymowitz on 2016-05-23T13:49:48Z says:_

(I hope I am doing this right.)

I have a recurring task for every Monday.

{code}
ID 6
Description remove the backup disk
Status Waiting
Recurrence weekly
Parent task 0b7de626-9df8-49f2-a01b-46472faad3cc
Mask Index 1
Entered 2016-05-23 09:23:19 (6min)
Waiting until 2016-05-30 01:00:00
Due 2016-05-30 09:00:00
Last modified 2016-05-19 08:21:05 (4d)
Tags sdo
Virtual tags CHILD MONTH TAGGED UNBLOCKED WAITING YEAR LATEST
UUID 36464447-9a4f-4c79-a972-b849f984f8e8
Urgency 3.409
{code}

Monday May 30th is a holiday. I would love a way to tell TaskWarrior that
* some tasks due on a holiday should be performed instead on the next business day
* some tasks due on a holiday should be performed instead on the previous business day.

Thanks.