datetime.date support in 0.8 new timeseries framework
Is is the intention that datetime.date would be supported as a valid input type for some methods? I have observed that it is only partially supported. Example, when using 0.8.0b1:

```
# Works
pandas.BDay().rollforward(datetime.date(2011, 11, 30))
# Doesn't work (returns None)
pandas.Day().rollforward(datetime.date(2011, 11, 30)) 

# Works
pandas.QuarterEnd().rollback(datetime.date(2011, 11, 30))
# Doesn't work (raises Exception, code expected datetime.datetime object)
pandas.YearEnd().rollback(datetime.date(2011, 11, 30)) 
```
