CLN: Remove pandas.tools module
Title is self-explanatory.

xref #15358.
xref #16005.
Hello @gfyoung! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/__init__.py`](https://github.com/gfyoung/pandas/blob/374bae0baae58b73b51bc920a34611f179db08c7/pandas/__init__.py) !

 - There are no PEP8 issues in the file [`pandas/plotting/_style.py`](https://github.com/gfyoung/pandas/blob/374bae0baae58b73b51bc920a34611f179db08c7/pandas/plotting/_style.py) !

 - There are no PEP8 issues in the file [`pandas/tests/api/test_api.py`](https://github.com/gfyoung/pandas/blob/374bae0baae58b73b51bc920a34611f179db08c7/pandas/tests/api/test_api.py) !

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23376?src=pr&el=h1) Report
> Merging [#23376](https://codecov.io/gh/pandas-dev/pandas/pull/23376?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/62a15fa4071d0711b2b97771b981d527c1c4af10?src=pr&el=desc) will **increase** coverage by `0.02%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23376/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23376?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #23376      +/-   ##
==========================================
+ Coverage   92.16%   92.19%   +0.02%     
==========================================
  Files         166      164       -2     
  Lines       51224    51198      -26     
==========================================
- Hits        47212    47200      -12     
+ Misses       4012     3998      -14
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.62% <ø> (+0.02%)` | :arrow_up: |
| #single | `42.23% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/23376?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/plotting/\_style.py](https://codecov.io/gh/pandas-dev/pandas/pull/23376/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19zdHlsZS5weQ==) | `77.41% <ø> (+2.41%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23376?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/23376?src=pr&el=footer). Last update [62a15fa...257c3b4](https://codecov.io/gh/pandas-dev/pandas/pull/23376?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 can you rebase @jreback : Rebased and green.  PTAL. thanks!