DOC: period missing at end of the pandas.DataFrame docstring

[jokuha]

Problem description

There is a full stop missing at the end of the pandas.DataFrame docstring.

Code Sample

import pandas as pd
help(pd.DataFrame)

Expected Output

Two-dimensional [...] The primary pandas data structure .

Output of pd.show_versions()

INSTALLED VERSIONS
--------------–--
commit: None
python: 3.6.3.final.0
python-bits: 64
OS: Darwin
OS-release: 17.3.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8

pandas: 0.22.0
pytest: None
pip: None
setuptools: 36.8.0
Cython: 0.27.3
numpy: 1.13.3
scipy: 1.0.0
pyarrow: None
xarray: None
IPython: 6.2.1
sphinx: 1.6.5
patsy: None
dateutil: 2.6.1
pytz: 2017.3
blosc: None
bottleneck: 1.2.1
tables: 3.4.2
numexpr: 2.6.4
feather: None
matplotlib: 0+unknown
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.10
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None

[databasedav]

I don't think the Numpy Docstring Standard explicitly requires periods. I took a quick look and other "core" classes (like Index and MultiIndex) are also missing periods at the end of their respective docstrings so if one wants to make this aesthetic change it would probably be best to write a script with the appropriate regular expression to put the periods where they aren't.