Bug22373: Enhance documentation for RangeIndex
Corrects documentation for RangeIndex and enhances documentation for RangeIndex and RangeIndex.from_range
closes #22373
passes `git diff upstream/master -u -- "*.py" | flake8 --diff`


Hello @mikapfl! Thanks for updating the PR.

 - There are no PEP8 issues in the file [`pandas/core/indexes/base.py`](https://github.com/mikapfl/pandas/blob/219f5ee93ee04e996dcbbac5db8d2f561d1a70ab/pandas/core/indexes/base.py) !

 - In the file [`pandas/core/indexes/range.py`](https://github.com/mikapfl/pandas/blob/219f5ee93ee04e996dcbbac5db8d2f561d1a70ab/pandas/core/indexes/range.py), following                are the PEP8 issues :
> [Line 42:80](https://github.com/mikapfl/pandas/blob/219f5ee93ee04e996dcbbac5db8d2f561d1a70ab/pandas/core/indexes/range.py#L42): [E501](https://duckduckgo.com/?q=pep8%20E501) line too long (82 > 79 characters)




##### Comment last updated on September 06, 2018 at 21:17 Hours UTC Agree that not including the stop of the range is standard, my point is that it's not obvious unless you know about this standard. So, I think it's worth mentioning it in the documentation.

If using the constructor is discouraged, we should also say it in the description I guess. # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22421?src=pr&el=h1) Report
> Merging [#22421](https://codecov.io/gh/pandas-dev/pandas/pull/22421?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/140c7bbda7aba8e9ac36a66a694234c9b1be4f95?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/22421/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/22421?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #22421   +/-   ##
=======================================
  Coverage   92.05%   92.05%           
=======================================
  Files         169      169           
  Lines       50714    50714           
=======================================
  Hits        46684    46684           
  Misses       4030     4030
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.46% <ø> (ø)` | :arrow_up: |
| #single | `42.25% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/22421?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexes/range.py](https://codecov.io/gh/pandas-dev/pandas/pull/22421/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9yYW5nZS5weQ==) | `95.7% <ø> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22421?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/22421?src=pr&el=footer). Last update [140c7bb...219f5ee](https://codecov.io/gh/pandas-dev/pandas/pull/22421?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @datapythonista I have added documentation and examples showing the half-inclusive behaviour of RangeIndex. The documentation is based on the python range documentation.

@jreback I have added langeuage and examples to Index and RangeIndex to guide users towards using Index(range(…)) instead of RangeIndex(…). @mikapfl could you rebase and merge master if you are still looking to take this on? If not I can potentially take a look @alimcmaster1, if you want to open a new PR with this. Closing as this seems abandoned.