ENH: Allow quantile to accept an int
This change is to allow `quantile` to accept an `int` argument to make it easier to compute a set of evenly-spaced quantiles.  For example, instead of typing `s.quantile([0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9])` or using `np.linspace` you can type `s.quantile(10)`.

- [ - ] closes #xxxx (no issue)
- [ x ] tests added / passed
- [ x ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ x ] whatsnew entry
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26350?src=pr&el=h1) Report
> Merging [#26350](https://codecov.io/gh/pandas-dev/pandas/pull/26350?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/bb0376c209d97e49b9c94038926ee62ddc0ee84d?src=pr&el=desc) will **decrease** coverage by `51.33%`.
> The diff coverage is `0%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26350/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26350?src=pr&el=tree)

```diff
@@             Coverage Diff             @@
##           master   #26350       +/-   ##
===========================================
- Coverage   92.04%   40.71%   -51.34%     
===========================================
  Files         175      175               
  Lines       52292    52296        +4     
===========================================
- Hits        48133    21291    -26842     
- Misses       4159    31005    +26846
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `?` | |
| #single | `40.71% <0%> (-0.15%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26350?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `34.46% <0%> (-62.68%)` | :arrow_down: |
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `45.51% <0%> (-48.16%)` | :arrow_down: |
| [pandas/io/formats/latex.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvbGF0ZXgucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/sas/sas\_constants.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXNfY29uc3RhbnRzLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/core/groupby/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9jYXRlZ29yaWNhbC5weQ==) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/tseries/plotting.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvcGxvdHRpbmcucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/tseries/converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/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/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvaHRtbC5weQ==) | `0% <0%> (-99.37%)` | :arrow_down: |
| [pandas/io/sas/sas7bdat.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXM3YmRhdC5weQ==) | `0% <0%> (-91.16%)` | :arrow_down: |
| [pandas/io/sas/sas\_xport.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXNfeHBvcnQucHk=) | `0% <0%> (-90.1%)` | :arrow_down: |
| ... and [132 more](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26350?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/26350?src=pr&el=footer). Last update [bb0376c...ea3b780](https://codecov.io/gh/pandas-dev/pandas/pull/26350?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/26350?src=pr&el=h1) Report
> Merging [#26350](https://codecov.io/gh/pandas-dev/pandas/pull/26350?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/bb0376c209d97e49b9c94038926ee62ddc0ee84d?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `75%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26350/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26350?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26350      +/-   ##
==========================================
- Coverage   92.04%   92.03%   -0.01%     
==========================================
  Files         175      175              
  Lines       52292    52293       +1     
==========================================
- Hits        48133    48130       -3     
- Misses       4159     4163       +4
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.59% <75%> (ø)` | :arrow_up: |
| #single | `40.72% <0%> (-0.16%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26350?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.02% <100%> (-0.12%)` | :arrow_down: |
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `93.58% <50%> (-0.09%)` | :arrow_down: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `78.94% <0%> (-10.53%)` | :arrow_down: |
| [pandas/core/arrays/integer.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2ludGVnZXIucHk=) | `96.33% <0%> (-0.03%)` | :arrow_down: |
| [pandas/core/dtypes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2Jhc2UucHk=) | `100% <0%> (ø)` | :arrow_up: |
| [pandas/core/internals/blocks.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2Jsb2Nrcy5weQ==) | `94.07% <0%> (ø)` | :arrow_up: |
| [pandas/core/dtypes/cast.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2Nhc3QucHk=) | `91.54% <0%> (ø)` | :arrow_up: |
| [pandas/core/dtypes/dtypes.py](https://codecov.io/gh/pandas-dev/pandas/pull/26350/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2R0eXBlcy5weQ==) | `96.66% <0%> (+0.23%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26350?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/26350?src=pr&el=footer). Last update [bb0376c...ecb84df](https://codecov.io/gh/pandas-dev/pandas/pull/26350?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 I'm not too fond of having the `q` parameter meaning 2 different things (the actual quantile(s) or a spacing). What's wrong with passing `np.linspace`? Agreed with https://github.com/pandas-dev/pandas/pull/26350#issuecomment-491638345 Ok, I'd been using the method a fair amount and felt it might make things more convenient in some cases, but could also see it causing confusion