BUG/DOC: searchsorted with sorter giving ValueError could not parse sorter
I get an error while building the docs with `searchsorted` (but there is not error on the travis docs, http://pandas-docs.github.io/pandas-docs-travis/basics.html#sorting-by-index-and-value):

```
In [22]: ser = Series([3, 1, 2])

In [23]: a = ser.values

In [24]: a.searchsorted([0,3], sorter=np.argsort(a))
Out[24]: array([0, 2])

In [25]: ser.searchsorted([0,3], sorter=np.argsort(ser))
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-25-d96921d13837> in <module>()
----> 1 ser.searchsorted([0,3], sorter=np.argsort(ser))

/home/joris/scipy/pandas/pandas/core/series.pyc in searchsorted(self, v, side, sorter)
   1431         """
   1432         return self.values.searchsorted(Series(v).values, side=side,
-> 1433                                         sorter=sorter)
   1434 
   1435     #------------------------------------------------------------------------------

ValueError: could not parse sorter argument

In [26]: pd.__version__ 
Out[26]: '0.14.1-641-gd65c9d7'

In [27]: np.__version__ 
Out[27]: '1.9.0'
```
