BUG: reducing ufuncs don't return a scalar
But are wrapped again in the Series or Index:

```
In [1]: s = pd.Series([1, 2, 3])

In [3]: np.add.reduce(s)
Out[3]: 
0    6
1    6
2    6
dtype: int64

In [4]: np.add.reduce(s.values)
Out[4]: 6
```