Implement deep copy option in Series.copy
Not quite sure if this is intentional behavior, but noticed that df.copy() accepts argument deep and series.copy() does not.  

> > > from pandas import Series, DataFrame
> > > s=Series([1,2,3])
> > > df=DataFrame(s)
> > > df.copy(deep=True)
> > >       0
> > >    0  1
> > >    1  2
> > >    2  3
> > > s.copy(deep=True)
> > >    Traceback (most recent call last):
> > >    File "<stdin>", line 1, in <module>
> > >     TypeError: copy() got an unexpected keyword argument 'deep'
