np.ndarray[object] - Timedelta raises

```
arr = np.array([pd.Timestamp.now(), pd.Timedelta('2D')])

>>> arr - pd.Timedelta('1D')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for -: 'numpy.ndarray' and 'Timedelta'
```

It should attempt to operate element-wise.