Dataframe.isin() doesnot work after upgrading to pandas 0.20.3
#### Code Sample, a copy-pastable example if possible

```python
 v=veh_frame.Accident_Index[(veh_frame.Accident_Index.isin(v2.tolist()))&(veh_frame.Vehicle_Type==11)]

```
#### Problem description

V2 is a series which is passed into the pandas dataframe. I have recently upgraded from pandas 0.19.1 to the latest stable release 0.20.3

In the previous version the series was passed as list and pandas was happy processing it, but now this throws an error with the Trace back as below

#### Output 

Traceback (most recent call last):

  File "<ipython-input-28-548ac2e79d56>", line 1, in <module>
    v=veh_frame.Accident_Index[(veh_frame.Accident_Index.isin(v2.tolist()))&(veh_frame.Vehicle_Type==11)]

  File "C:\Users\TRLuser\Anaconda3\lib\site-packages\pandas\core\series.py", line 2555, in isin
    result = algorithms.isin(_values_from_object(self), values)

  File "C:\Users\TRLuser\Anaconda3\lib\site-packages\pandas\core\algorithms.py", line 426, in isin
    return f(comps, values)

  File "C:\Users\TRLuser\Anaconda3\lib\site-packages\pandas\core\algorithms.py", line 406, in <lambda>
    f = lambda x, y: np.in1d(x, y)

  File "C:\Users\TRLuser\Anaconda3\lib\site-packages\numpy\lib\arraysetops.py", line 401, in in1d
    ar2 = np.unique(ar2)

  File "C:\Users\TRLuser\Anaconda3\lib\site-packages\numpy\lib\arraysetops.py", line 214, in unique
    ar.sort()

TypeError: '>' not supported between instances of 'int' and 'str'



#### Output of ``pd.show_versions()``

<details>
INSTALLED VERSIONS
------------------
commit: None
python: 3.6.1.final.0
python-bits: 64
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 158 Stepping 9, GenuineIntel
byteorder: little
LC_ALL: None
LANG: en
LOCALE: None.None

pandas: 0.20.3
pytest: 3.0.7
pip: 9.0.1
setuptools: 27.2.0
Cython: 0.25.2
numpy: 1.12.1
scipy: 0.19.0
xarray: None
IPython: 5.3.0
sphinx: 1.5.6
patsy: 0.4.1
dateutil: 2.6.0
pytz: 2017.2
blosc: None
bottleneck: 1.2.1
tables: 3.2.2
numexpr: 2.6.2
feather: None
matplotlib: 2.0.2
openpyxl: 2.4.7
xlrd: 1.0.0
xlwt: 1.2.0
xlsxwriter: 0.9.6
lxml: 3.7.3
bs4: 4.6.0
html5lib: 0.999
sqlalchemy: 1.1.9
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
pandas_gbq: None
pandas_datareader: None


</details>
