Unable to compare timedelta64 to timedelta
```
In [426]:
s = pd.Series([timedelta(days=1), timedelta(days=2)])
s > timedelta(days=1)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-426-9094b7c93677> in <module>()
      1 s = pd.Series([timedelta(days=1), timedelta(days=2)])
----> 2 s > timedelta(days=1)

/usr/local/lib/python2.7/dist-packages/pandas-0.13.0rc1_78_g142ca62-py2.7-linux-x86_64.egg/pandas/core/ops.pyc in wrapper(self, other)
    561 
    562             # scalars
--> 563             res = na_op(values, other)
    564             if np.isscalar(res):
    565                 raise TypeError('Could not compare %s type with Series'

/usr/local/lib/python2.7/dist-packages/pandas-0.13.0rc1_78_g142ca62-py2.7-linux-x86_64.egg/pandas/core/ops.pyc in na_op(x, y)
    528 
    529             try:
--> 530                 result = getattr(x, name)(y)
    531                 if result is NotImplemented:
    532                     raise TypeError("invalid type comparison")

TypeError: can't compare datetime.timedelta to long
```

The comparison does work for `timedelta64`:

```
In [45]: s > np.timedelta64(timedelta(days=1))
Out[45]: 
0    False
1     True
dtype: bool
```
