DOC: Fix various warnings
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/20509?src=pr&el=h1) Report
> Merging [#20509](https://codecov.io/gh/pandas-dev/pandas/pull/20509?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/9b4d0f13a6dba19ff1e1d8b404837eaad600c863?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/20509/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/20509?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #20509      +/-   ##
==========================================
- Coverage   91.84%   91.84%   -0.01%     
==========================================
  Files         152      152              
  Lines       49261    49260       -1     
==========================================
- Hits        45245    45244       -1     
  Misses       4016     4016
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.23% <100%> (-0.01%)` | :arrow_down: |
| #single | `41.9% <100%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/20509?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/20509/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `95.85% <ø> (ø)` | :arrow_up: |
| [pandas/plotting/\_core.py](https://codecov.io/gh/pandas-dev/pandas/pull/20509/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb3JlLnB5) | `82.5% <ø> (ø)` | :arrow_up: |
| [pandas/util/\_decorators.py](https://codecov.io/gh/pandas-dev/pandas/pull/20509/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvX2RlY29yYXRvcnMucHk=) | `82.25% <100%> (-0.15%)` | :arrow_down: |
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/20509/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `93.85% <100%> (ø)` | :arrow_up: |
| [pandas/core/strings.py](https://codecov.io/gh/pandas-dev/pandas/pull/20509/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc3RyaW5ncy5weQ==) | `98.32% <0%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/20509?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/20509?src=pr&el=footer). Last update [9b4d0f1...d6eaf5f](https://codecov.io/gh/pandas-dev/pandas/pull/20509?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 OK, if this all passes I think it's ready. There are still a few warnings left, but those are more involved. I added a toctree for the docstring guide. Here's the rendered version

![screen shot 2018-03-28 at 1 21 42 pm](https://user-images.githubusercontent.com/1312546/38048464-0beedbb4-328b-11e8-8e2c-cd34785329d1.png)
