DOC: update the to_excel 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

```
Errors found:
	Missing description for See Also "pd.read_excel" reference
```
@cmdelatorre I'm aware this is an incomplete PR and I'm sorry about that but we ran out of time on the sprint. I've added an extended summary covering the basics. # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/20185?src=pr&el=h1) Report
> Merging [#20185](https://codecov.io/gh/pandas-dev/pandas/pull/20185?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/3e4839301fc2927646889b194c9eb41c62b76bda?src=pr&el=desc) will **decrease** coverage by `0.17%`.
> The diff coverage is `93.33%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/20185/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/20185?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #20185      +/-   ##
==========================================
- Coverage      92%   91.82%   -0.18%     
==========================================
  Files         170      153      -17     
  Lines       50609    49256    -1353     
==========================================
- Hits        46561    45229    -1332     
+ Misses       4048     4027      -21
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.21% <93.33%> (-0.2%)` | :arrow_down: |
| #single | `41.9% <23.33%> (-0.29%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/20185?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/20185/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `95.94% <93.33%> (-0.53%)` | :arrow_down: |
| [pandas/util/\_doctools.py](https://codecov.io/gh/pandas-dev/pandas/pull/20185/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvX2RvY3Rvb2xzLnB5) | `0% <0%> (-12.88%)` | :arrow_down: |
| [pandas/core/arrays/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/20185/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2Jhc2UucHk=) | `84.14% <0%> (-3.72%)` | :arrow_down: |
| [pandas/io/formats/printing.py](https://codecov.io/gh/pandas-dev/pandas/pull/20185/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvcHJpbnRpbmcucHk=) | `89.38% <0%> (-3.71%)` | :arrow_down: |
| [pandas/core/groupby/groupby.py](https://codecov.io/gh/pandas-dev/pandas/pull/20185/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9ncm91cGJ5LnB5) | `92.55% <0%> (-3.58%)` | :arrow_down: |
| [pandas/core/dtypes/missing.py](https://codecov.io/gh/pandas-dev/pandas/pull/20185/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL21pc3NpbmcucHk=) | `91.07% <0%> (-2.5%)` | :arrow_down: |
| [pandas/core/reshape/tile.py](https://codecov.io/gh/pandas-dev/pandas/pull/20185/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS90aWxlLnB5) | `93.37% <0%> (-1.37%)` | :arrow_down: |
| [pandas/core/indexes/interval.py](https://codecov.io/gh/pandas-dev/pandas/pull/20185/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9pbnRlcnZhbC5weQ==) | `93.08% <0%> (-1.05%)` | :arrow_down: |
| [pandas/plotting/\_core.py](https://codecov.io/gh/pandas-dev/pandas/pull/20185/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb3JlLnB5) | `82.5% <0%> (-0.99%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/20185/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `84.73% <0%> (-0.96%)` | :arrow_down: |
| ... and [94 more](https://codecov.io/gh/pandas-dev/pandas/pull/20185/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/20185?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/20185?src=pr&el=footer). Last update [3e48393...b2a6496](https://codecov.io/gh/pandas-dev/pandas/pull/20185?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 I've completely wiped by env to try and fix this error but still it persists. Means I am not able to run the validation script:
```
(pandas_dev) Robins-MacBook-Air:pandas robincole$ python scripts/validate_docstrings.py pandas.DataFrame.to_excel
Traceback (most recent call last):
  File "scripts/validate_docstrings.py", line 37, in <module>
    import pandas
  File "/Users/robincole/Documents/Github/pandas/pandas/__init__.py", line 42, in <module>
    from pandas.core.api import *
  File "/Users/robincole/Documents/Github/pandas/pandas/core/api.py", line 10, in <module>
    from pandas.core.groupby import Grouper
  File "/Users/robincole/Documents/Github/pandas/pandas/core/groupby.py", line 48, in <module>
    from pandas.core.frame import DataFrame
  File "/Users/robincole/Documents/Github/pandas/pandas/core/frame.py", line 75, in <module>
    from pandas.core.series import Series
  File "/Users/robincole/Documents/Github/pandas/pandas/core/series.py", line 115, in <module>
    class Series(base.IndexOpsMixin, generic.NDFrame):
  File "/Users/robincole/Documents/Github/pandas/pandas/core/series.py", line 2942, in Series
    @Appender(generic._shared_docs['to_excel'] % _shared_doc_kwargs)
TypeError: not enough arguments for format string
```
Hopefully I can fix this Hello @robmarkcole! Thanks for updating the PR.



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

##### Comment last updated on July 24, 2018 at 16:02 Hours UTC @robmarkcole were you able to sort out your issues? That error means that you're failing to pass a keyword to some other place that's using this shared docstring. Do you have time to finish this off? @tomaugspurger I want able to solve and an not sure how I will. I am on holiday this week without computer so will have to take a look next week. Sorry for the delay See my comment here https://github.com/pandas-dev/pandas/pull/20185#discussion_r174501036 for a solution. 

> Sorry for the delay

No problem! @TomAugspurger @jorisvandenbossche sorry this fell off my radar after my holiday, have addressed your comments now. I'm still unable to run the validation script but hopefully all changes are OK Thanks @robmarkcole!