add a function to get hour_of_year

[timmichelsen]

Please add the following functionality to tdates.py / DateArray?. This could be a good addition to DateArray?.day_of_year / DateArray?.yeardays

def alt_hoyt(datearr):
     return (datearr.day_of_year-1)*24+datearr.hour

Also, the following functions would help:

minute_of_day minute_of_year

refer to http://permalink.gmane.org/gmane.comp.python.scientific.user/18478

Thanks in advance.