- Added note about force pushing same branch to update a existing pull
  request instead of opening new one in contributing guide.
- [ci skip]

[ci skip]

I have seen many times that maintainers want people to use this gem to give
a benchmark report. It would be nice to add it and refer to it later.

[ci skip]

This reverts commit fe985960, reversing
changes made to add95606.

This commit adds new lines between titles, paragraphs and code blocks
for an easier reading.

Moreover, in order to be consistent with the other guides, let's remove
the sharps on the right side of the different titles.

The "Running a Single Test" part was also explained after the "Testing
Active Record" one which shows how to run a single test under the scope
of a specific adapter.

Finally, let's explain the `-n` option to run a specific test method.

This reverts commit 28bd4420.

Reason: Existing text was clearer imo.

[ci skip]

[ci skip]

[ci skip]

Including replacing a few "smart quotes" with regular quotes (' and "),
for consistency.
[ci skip]

Logically group the content, so it makes more sense if someone tries to read from start of page to end of page. [ci skip]

- Manually applied from #13951.
- Discussion at #13947.
- Removed trailing whitespace from https://github.com/dpmehta02/rails/commit/18044e86af93672dfc38befbe974261e87b3518d

/cc @dpmehta02

This reverts commit 41ba51f4.

[ci skip]

Escape hyphen

[ci skip]

Sometimes people ask what makes a feature and what makes a bug, so
let's clarify that so we can show it to people later.

I don't know of anyone that hangs out in #rails-contrib, and we should
also let people know that feedback can take some time.

Many people don't, so point them to a place where they can meet
some.

[ci skip]

Follow-up to #11934

link break added after the Travis CI link

This reverts commit 6df9c595.

Changing links to guides.

We are not worried for old versions as GitHub is 
handling the redirects.