PERF: expand asv benchmark coverage
Continuing on the approach in #23935, I've identified significant functions with no benchmark coverage in the `asv` suite - this time extending the line tracing analysis down to the Cython layer. Of interest:

- `merge_asof()` is only benchmarked in the default direction, despite the other two directions having unique Cython codepaths
- Reindex operations on a `PeriodIndex` are currently largely uncovered
- `CategoricalIndex` is missing a lot of basic cases
- There's a chunk of Cython code specifically for parsing `Quarter` strings that now has a benchmark
 - Several typos in the `Timestamp` benchmarks

I'll update this comment when the `asv` comparison runs complete.

- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @qwhelan! Thanks for updating the PR.





 - In the file [`asv_bench/benchmarks/join_merge.py`](https://github.com/pandas-dev/pandas/blob/ce6bed2bbc57351d1d08cfd8a3962426f74ec6a8/asv_bench/benchmarks/join_merge.py), following are the PEP8 issues :

> [Line 284:80](https://github.com/pandas-dev/pandas/blob/ce6bed2bbc57351d1d08cfd8a3962426f74ec6a8/asv_bench/benchmarks/join_merge.py#L284): [E501](https://duckduckgo.com/?q=pep8%20E501) line too long (90 > 79 characters)
> [Line 332:80](https://github.com/pandas-dev/pandas/blob/ce6bed2bbc57351d1d08cfd8a3962426f74ec6a8/asv_bench/benchmarks/join_merge.py#L332): [E501](https://duckduckgo.com/?q=pep8%20E501) line too long (83 > 79 characters)

















##### Comment last updated on January 08, 2019 at 21:23 Hours UTC # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24214?src=pr&el=h1) Report
> Merging [#24214](https://codecov.io/gh/pandas-dev/pandas/pull/24214?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/1ae466c7d777fe303461946eb5a3ff9ee78b9c73?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24214/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24214?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24214      +/-   ##
==========================================
- Coverage   92.37%   92.37%   -0.01%     
==========================================
  Files         166      166              
  Lines       52315    52315              
==========================================
- Hits        48328    48327       -1     
- Misses       3987     3988       +1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.79% <ø> (ø)` | :arrow_up: |
| #single | `43.06% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24214?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/24214/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `88% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24214?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/24214?src=pr&el=footer). Last update [1ae466c...014fea3](https://codecov.io/gh/pandas-dev/pandas/pull/24214?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24214?src=pr&el=h1) Report
> Merging [#24214](https://codecov.io/gh/pandas-dev/pandas/pull/24214?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/91802fb0accde031c3b6aca040a8b533a193fef6?src=pr&el=desc) will **decrease** coverage by `49.2%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24214/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24214?src=pr&el=tree)

```diff
@@             Coverage Diff             @@
##           master   #24214       +/-   ##
===========================================
- Coverage   92.21%      43%   -49.21%     
===========================================
  Files         162      162               
  Lines       51763    51763               
===========================================
- Hits        47733    22261    -25472     
- Misses       4030    29502    +25472
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `?` | |
| #single | `43% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24214?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/formats/latex.py](https://codecov.io/gh/pandas-dev/pandas/pull/24214/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvbGF0ZXgucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/core/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/24214/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY2F0ZWdvcmljYWwucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/sas/sas\_constants.py](https://codecov.io/gh/pandas-dev/pandas/pull/24214/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXNfY29uc3RhbnRzLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/tseries/plotting.py](https://codecov.io/gh/pandas-dev/pandas/pull/24214/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvcGxvdHRpbmcucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/tseries/converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/24214/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvY29udmVydGVyLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/formats/html.py](https://codecov.io/gh/pandas-dev/pandas/pull/24214/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvaHRtbC5weQ==) | `0% <0%> (-98.62%)` | :arrow_down: |
| [pandas/core/groupby/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/24214/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9jYXRlZ29yaWNhbC5weQ==) | `0% <0%> (-95.46%)` | :arrow_down: |
| [pandas/io/sas/sas7bdat.py](https://codecov.io/gh/pandas-dev/pandas/pull/24214/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXM3YmRhdC5weQ==) | `0% <0%> (-91.17%)` | :arrow_down: |
| [pandas/io/sas/sas\_xport.py](https://codecov.io/gh/pandas-dev/pandas/pull/24214/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXNfeHBvcnQucHk=) | `0% <0%> (-90.15%)` | :arrow_down: |
| [pandas/core/tools/numeric.py](https://codecov.io/gh/pandas-dev/pandas/pull/24214/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvdG9vbHMvbnVtZXJpYy5weQ==) | `10.44% <0%> (-89.56%)` | :arrow_down: |
| ... and [119 more](https://codecov.io/gh/pandas-dev/pandas/pull/24214/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24214?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/24214?src=pr&el=footer). Last update [91802fb...5549d6b](https://codecov.io/gh/pandas-dev/pandas/pull/24214?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 can you merge master and update @WillAyd Rebased and incorporated your comments some linting issues:https://dev.azure.com/pandas-dev/pandas/_build/results?buildId=6625 @jreback I've added a small `asv` suite fix - a recent change to `pandas_vb_common.py` means the suite will completely fail on init for any commits prior to ~July when the EA Dtypes were added. lgtm. over to you @WillAyd  Thanks @qwhelan !