DOC: spellchecked io.rst
Spellcheck of the docs, specifically of `io.rst`.
I did not read everything thoroughly, but I believe the suggested changes will help enforce a greater level of consistency in the docs.

* Backticks ` `` ` around Series, DataFrame.
* Added some function references, i.e. `` :meth:`~DataFrame.method` ``.
* Consistency of booleans, typsetting as ``False`` instead of False or *False*.
* Minor rephrasing of sentences, spelling, periods, colons etc.

Cheers!

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19660?src=pr&el=h1) Report
> Merging [#19660](https://codecov.io/gh/pandas-dev/pandas/pull/19660?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/569bc7a35c06ef8eb9a121ca983ba8951399a124?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/19660/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/19660?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #19660      +/-   ##
==========================================
+ Coverage   91.58%   91.59%   +<.01%     
==========================================
  Files         150      150              
  Lines       48806    48806              
==========================================
+ Hits        44701    44703       +2     
+ Misses       4105     4103       -2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.96% <ø> (ø)` | :arrow_up: |
| #single | `41.73% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/19660?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/19660/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `83.85% <0%> (+0.2%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19660?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/19660?src=pr&el=footer). Last update [569bc7a...9bd5a5b](https://codecov.io/gh/pandas-dev/pandas/pull/19660?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks @tommyod 

I kind of like the formatting when reading with quoted DataFrame/Series.