Alignment of CategoricalIndex
#### Code Sample, a copy-pastable example if possible

```
In [2]: c = pd.CategoricalIndex(['3z53', '3z53', 'LoJG', 'LoJG', 'LoJG', 'N503'])

In [3]: s1 = pd.Series(2, index=c)

In [4]: s2 = pd.Series(2, index=c[:-1])

In [5]: s1*s2
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-5-7426096cfe41> in <module>()
----> 1 s1*s2

/home/pietro/nobackup/repo/pandas/pandas/core/ops.py in wrapper(left, right, name, na_op)
    647             else:
    648                 index, lidx, ridx = left.index.join(rindex, how='outer',
--> 649                                                     return_indexers=True)
    650 
    651                 if lidx is not None:

/home/pietro/nobackup/repo/pandas/pandas/indexes/base.py in join(self, other, how, level, return_indexers)
   2524         if not self.is_unique and not other.is_unique:
   2525             return self._join_non_unique(other, how=how,
-> 2526                                          return_indexers=return_indexers)
   2527         elif not self.is_unique or not other.is_unique:
   2528             if self.is_monotonic and other.is_monotonic:

/home/pietro/nobackup/repo/pandas/pandas/indexes/base.py in _join_non_unique(self, other, how, return_indexers)
   2616         join_index = self.values.take(left_idx)
   2617         mask = left_idx == -1
-> 2618         np.putmask(join_index, mask, other._values.take(right_idx))
   2619 
   2620         join_index = self._wrap_joined_index(join_index, other)

TypeError: putmask() argument 1 must be numpy.ndarray, not Categorical
```
#### Expected Output

No error
#### output of `pd.show_versions()`

```
In [6]: pd.show_versions()

INSTALLED VERSIONS
------------------
commit: None
python: 3.5.1.final.0
python-bits: 64
OS: Linux
OS-release: 4.5.0-2-amd64
machine: x86_64
processor: 
byteorder: little
LC_ALL: None
LANG: it_IT.utf8

pandas: 0.18.1+102.g0c6226c
nose: 1.3.7
pip: 1.5.6
setuptools: 18.4
Cython: 0.23.4
numpy: 1.10.4
scipy: 0.16.0
statsmodels: 0.8.0.dev0+0fac349
xarray: None
IPython: 5.0.0.dev
sphinx: 1.3.1
patsy: 0.3.0-dev
dateutil: 2.2
pytz: 2012c
blosc: None
bottleneck: 1.1.0dev
tables: 3.2.2
numexpr: 2.5
matplotlib: 1.5.1
openpyxl: None
xlrd: 0.9.4
xlwt: None
xlsxwriter: 0.7.3
lxml: None
bs4: 4.4.0
html5lib: 0.999
httplib2: 0.9.1
apiclient: 1.5.0
sqlalchemy: 1.0.11
pymysql: None
psycopg2: None
jinja2: 2.8
boto: 2.38.0
pandas_datareader: 0.2.1
```
