DOC: update the pandas.Series.dt.is_year_end docstring
Checklist for the pandas documentation sprint (ignore this if you are doing
an unrelated PR):

- [X] PR title is "DOC: update the <your-function-or-method> docstring"
- [X] The validation script passes: `scripts/validate_docstrings.py <your-function-or-method>`
- [X] The PEP8 style check passes: `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [X] The html version looks good: `python doc/make.py --single <your-function-or-method>`
- [X] 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_year_end) ###################
################################################################################

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

Returns
-------
is_year_end : Series of boolean.

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

Examples
--------
>>> dates = pd.Series(pd.date_range("2017-12-30", periods=3))
>>> dates
0   2017-12-30
1   2017-12-31
2   2018-01-01
dtype: datetime64[ns]
>>> dates.dt.is_year_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

Hello @janelle! Thanks for updating the PR.

 - In the file [`pandas/core/indexes/datetimes.py`](https://github.com/pandas-dev/pandas/blob/61aedbc4780130d250d440f6e4398418ab481025/pandas/core/indexes/datetimes.py), following are the PEP8 issues :

> [Line 1793:80](https://github.com/pandas-dev/pandas/blob/61aedbc4780130d250d440f6e4398418ab481025/pandas/core/indexes/datetimes.py#L1793): [E501](https://duckduckgo.com/?q=pep8%20E501) line too long (80 > 79 characters)



##### Comment last updated on March 14, 2018 at 18:55 Hours UTC Updated. Fixed some some See Alsos in the other docstrings where we said `method` instead of `property`.

Thanks again @janelle!