ERR: Remove bitwise operations on dtype=object?
#### Code Sample, a copy-pastable example if possible

```python

1) This is okay:

~pd.Series([False, False, True, False], dtype=bool)

Out[76]:
0     True
1     True
2    False
3     True
dtype: bool

2) This looks like a problem:

~pd.Series([False, False, True, False], dtype=bool).shift(1).dropna()
1    -1
2    -1
3    -2
dtype: object
```

#### Problem description

`.shift` and `.dropna` are common pandas operations.

.shift(1) converts dtype from bool to object, so the bitwise operation is applied to each object (~False).

The output in the latter case is extremely surprising. It might be safer to raise an Exception rather than allow bitwise operations implemented on objects.

~pd.Series([1.0], dtype=object)

#### Expected Output

Exception!

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

<details>
INSTALLED VERSIONS
------------------
commit: None
python: 2.7.13.final.0
python-bits: 64
OS: Linux
OS-release: 4.10.0-21-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: None.None

pandas: 0.19.0
nose: 1.3.7
pip: 9.0.1
setuptools: 35.0.2
Cython: 0.25.1
numpy: 1.10.1
scipy: 0.16.0
statsmodels: 0.6.1
xarray: None
IPython: 5.3.0
sphinx: 1.2.2
patsy: 0.4.0
dateutil: 2.6.0
pytz: 2015.6
blosc: None
bottleneck: None
tables: 3.3.0
numexpr: 2.4.6
matplotlib: 2.0.1
openpyxl: 2.3.3
xlrd: 0.9.4
xlwt: None
xlsxwriter: 0.8.4
lxml: 3.5.0
bs4: 4.5.3
html5lib: 0.999999999
httplib2: 0.9.2
apiclient: 1.4.2
sqlalchemy: 1.0.8
pymysql: None
psycopg2: None
jinja2: 2.9.6
boto: 2.20.1
pandas_datareader: None

</details>
