CLN: ASV plotting
Flake8'd and simplified some of the setup. 

```
$ asv dev -b ^plotting
· Discovering benchmarks
· Running 6 total benchmarks (1 commits * 1 environments * 6 benchmarks)
[  0.00%] ·· Building for existing-py_home_matt_anaconda_envs_pandas_dev_bin_python
[  0.00%] ·· Benchmarking existing-py_home_matt_anaconda_envs_pandas_dev_bin_python
[ 16.67%] ··· Running plotting.Misc.time_plot_andrews_curves              1.92s
[ 33.33%] ··· Running plotting.Plotting.time_frame_plot                   417ms
[ 50.00%] ··· Running plotting.Plotting.time_series_plot                  418ms
[ 66.67%] ··· Running ...ting.TimeseriesPlotting.time_plot_irregular      130ms
[ 83.33%] ··· Running plotting.TimeseriesPlotting.time_plot_regular       388ms
[100.00%] ··· Running ...TimeseriesPlotting.time_plot_regular_compat      123ms
```

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18916?src=pr&el=h1) Report
> Merging [#18916](https://codecov.io/gh/pandas-dev/pandas/pull/18916?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/6164da24a7d3f9469fcad8b987c9c7fac1c8dd25?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18916/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/18916?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #18916   +/-   ##
=======================================
  Coverage   91.65%   91.65%           
=======================================
  Files         154      154           
  Lines       51368    51368           
=======================================
  Hits        47080    47080           
  Misses       4288     4288
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.52% <ø> (ø)` | :arrow_up: |
| #single | `40.84% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18916?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/18916?src=pr&el=footer). Last update [6164da2...a721635](https://codecov.io/gh/pandas-dev/pandas/pull/18916?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks!