COMPAT: datetime.date comparisons with datetime64[ns]
This should probably work
```
In [16]: df = pd.DataFrame({'A':[pd.Timestamp('20130101'), np.nan]})

In [17]: df
Out[17]: 
           A
0 2013-01-01
1        NaT

In [18]: pd.Timestamp('20130101').to_pydatetime()>=df.A
Out[18]: 
0     True
1    False
Name: A, dtype: bool

In [20]: pd.Timestamp('20130101').to_pydatetime().date()>=df.A
ValueError: cannot set a Timestamp with a non-timestamp
```