DOC: Exception in timeseries due to int64 __floordiv__
http://pandas-docs.github.io/pandas-docs-travis/timeseries.html#from-timestamps-to-epoch

```python
In [3]: stamps = pd.date_range('2012-10-08 18:15:05', periods=4, freq='D')
   ...: stamps.view('int64') // pd.Timedelta(1, unit='s')
   ...:
```

```pytb
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-3-e2a3bb41d0d7> in <module>()
      1 stamps = pd.date_range('2012-10-08 18:15:05', periods=4, freq='D')
----> 2 stamps.view('int64') // pd.Timedelta(1, unit='s')

~/sandbox/pandas-ip/pandas/pandas/_libs/tslibs/timedeltas.pyx in pandas._libs.tslibs.timedeltas.Timedelta.__rfloordiv__()
   1189                 # also timedelta-like
   1190                 return _broadcast_floordiv_td64(self.value, other, _rfloordiv)
-> 1191             raise TypeError('Invalid dtype {dtype} for '
   1192                             '{op}'.format(dtype=other.dtype,
   1193                                           op='__floordiv__'))

TypeError: Invalid dtype int64 for __floordiv__
```