DOC: update the pandas.Series.dt.is_month_end docstring

[janelle]

Checklist for the pandas documentation sprint (ignore this if you are doing
an unrelated PR):

• PR title is "DOC: update the docstring"
• The validation script passes: scripts/validate_docstrings.py <your-function-or-method>
• The PEP8 style check passes: git diff upstream/master -u -- "*.py" | flake8 --diff
• The html version looks good: python doc/make.py --single <your-function-or-method>
• It has been proofread on language by another sprint participant

Please include the output of the validation script below between the "```" ticks:

################################################################################
################## Docstring (pandas.Series.dt.is_month_end)  ##################
################################################################################

Return a boolean indicating whether the date is the last day of the month.

Returns
-------
is_month_end : Series of boolean.

See Also
--------
is_month_start : Return a boolean indicating whether the date is
    the first day of the month.

Examples
--------
>>> dates = pd.Series(pd.date_range("2018-02-27", periods=3))
>>> dates
0   2018-02-27
1   2018-02-28
2   2018-03-01
dtype: datetime64[ns]
>>> dates.dt.is_month_end
0    False
1    True
2    False
dtype: bool

################################################################################
################################## Validation ##################################
################################################################################

Errors found:
	No extended summary found

If the validation script still gives errors, but you think there is a good reason
to deviate in this case (and there are certainly such cases), please state this
explicitly.

No extended summary required in this case (as confirmed with peers).

[pep8speaks]

Hello @janelle! Thanks for updating the PR.

Cheers ! There are no PEP8 issues in this Pull Request. 🍻

Comment last updated on March 17, 2018 at 11:56 Hours UTC

[Cheukting]

The sentences for See Also section is too long, need to break it into 2 lines.

[codecov]

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Flag	Coverage Δ
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pandas/core/indexes/datetimes.py	95.64% <ø> (ø)

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[jorisvandenbossche]

Looks good!

Added a commit that fixes the PEP8 issues, and added an example with an index (the docstring is shared between Series.dt and DatetimeIndex)

[jorisvandenbossche]

Thanks @janelle !