Setting day of week with week start as Sunday:

>>> from xix.utils.timetool import setDayOfWeek, SUNDAY, SATURDAY
>>> from time import strptime, strftime, mktime, tzset
>>> from datetime import datetime
>>> t = strptime('2005-11-29', '%Y-%m-%d')
>>> dt = datetime.fromtimestamp(mktime(t))
>>> dt2 = setDayOfWeek(dt, SUNDAY, startsun=True)
>>> print strftime('%Y-%m-%d', dt2.timetuple())
2005-11-27
>>> dt2 = setDayOfWeek(dt, SATURDAY, startsun=True)
>>> print strftime('%Y-%m-%d', dt2.timetuple())
2005-12-03

