DOC: Python Package for Pandas Documentation
#### Problem description

It would be a nice enhancement if the documentation for pandas could be installed with pip from a PyPI package. This would make it easier to maintain a local copy of the pandas documentation aligned with the installed version of the pandas library.

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

<details>

INSTALLED VERSIONS
------------------
commit: None
python: 2.7.5.final.0
python-bits: 64
OS: Linux
OS-release: 3.10.0-693.2.2.el7.x86_64
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.utf8
LOCALE: None.None

pandas: 0.20.3
pytest: 3.2.2
pip: 9.0.1
setuptools: 36.5.0
Cython: None
numpy: 1.13.1
scipy: None
xarray: None
IPython: 5.5.0
sphinx: None
patsy: None
dateutil: 2.6.1
pytz: 2017.2
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: None
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: 1.0b10
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
pandas_gbq: None
pandas_datareader: None

</details>
