Minor fix to #28662

[ci skip]

To allow easy linking at all levels and not just from index

Fixes #25744 by slightly increasing the margin in code syntax
highlights. With a margin of 0, it was cutting off underscores in Linux
browesers, so I slightly increased it to 0.5px.

- Build Syntax Highlighter based on https://github.com/syntaxhighlighter/syntaxhighlighter/wiki/Building and use theme generated by fxn.
- This also bundles these brushes in the file itself- ruby,css,xml,sql,javascript,plain. Generation command used:
gulp build --compat --brushes=javascript,ruby,xml,sql,plain --theme=/Path/To/RailsSource/rails/guides/assets/stylesheets/syntaxhighlighter/shThemeRailsGuides.css
- rm all old js and css files
- Moved over how JS configuration is created for Syntax Highlighter
- Fixed layout for all imports
- Fixes bug with old copy paste, generating wrong space character on webkit https://github.com/syntaxhighlighter/syntaxhighlighter/blob/7caa9632e7fe470d944fc06b4db7d35352ebaa36/src/dom.js#L227

 Fixes #25655

- Rails 5 will return 204 No Content by default for controller actions
  which do not have a template or do not specify how to render.
- The "Getting started" guide needs to be updated for this.

Selectively add `li ul, li ol { margin:0 1.5em; }` to subColl needed for Chapters column, instead of leaking to other lists.

Before:
 https://monosnap.com/file/CNIMXcqv3HuRrObTNYWYFis8I3G8PT
After:
 https://monosnap.com/file/0IyEKEy9hcRCIx82etR8ikinCo3vNb

Chapters column remains as is: http://take.ms/M0BkF

Change background-color value to transparent, which is the default value of background-color.

[ci skip]

As requested by David in 23233.

changed from 755 to 644.
I executed `chmod -x guides/assets/javascripts/responsive-tables.js`.
[ci skip]

- Add new logo for guides header
[ci skip]

fixes #21500

[ci skip]

Change all of anchor text in the nav links to `Back` and `Edit`
Use `Edit | Back` on pages that use both links to conform to what
scaffolding generates.

Use consistent anchor text throughout the guide.

Change all of anchor text in the nav links to `Back` and `Edit`
Use `Edit | Back` on pages that use both links to conform to what
scaffolding generates.

Commit 65a2977c added a `pre-wrap` style for white spaces on `.note`
paragraphs. However, this is first inconsistent as other notes like
warnings don't have this style applied. Furthermore, it seems to be
unneeded for mobile devices.

Also revert changes made in #18147 since they aren't needed anymore.

Cross-refs #18138.

[ci skip]

/cc @chancancode @robin850

configuration reference: http://alexgorbatchev.com/SyntaxHighlighter/manual/configuration/

Related issues:

* https://github.com/vmg/redcarpet/issues/334

* https://github.com/docrails-tw/guides/issues/62

We noticed the rails gem increased in size between the beta and rc
versions, and the reason is that some guides images were updated but not
properly optimized, and one image changed from png to jpg, way bigger.

Converting the jpg image back to png, and using ImageOptim to optimize
all the images for web view, improves the situation [ci skip].

---

In current master/4-1-stable:

    508K  guides/assets/images/getting_started/

In v4.1.0.beta1:

    268K  guides/assets/images/getting_started/

In 4-0-stable

    328K  guides/assets/images/getting_started/

After the patch:

    260K  guides/assets/images/getting_started/

- Used Article model instead of Post as it may confuse with 'post'
  requests
- Tried to wrap the guide to 80 chars lines as much as possible.
- Removed unused image
- Fixes #13764

More to come.

I had written the original guide for "A Guide to Testing Rails
Applications". The current documents maintains the same structure and
examples I had drafted albeit with some minor changes to keep up with
newer version of Rails.

Older version which had credits included:
http://guides.rubyonrails.org/v2.3.11/testing.html

Github lifo/docrails History:
https://github.com/rails/rails/commits/ff359af86505b4d317b7467e7f79aa2ef2c5e795/railties/doc/guides/source/testing_rails_applications.txt

dropdown menu on guides page (which appear on small windows)
[ci skip]

* Stop using unnecessary global variable
* Use function defined by jQuery for simplicity
* Fix event listner for "more info button" to handle
  event on resize browser

This reverts commit 91a1cf70.

Reason: code changes disallowed in docrails, even if they are
guides generation related.

Used imageoptim, Saved few bytes
http://imageoptim.com/

Move 2 images to getting_started folder. All other images in getting started guide already in this folder.

When I updated these images, I must have gotten this one wrong. Now it's
right.

Fixes #9749.

Stuff didn't work because of strong_parameters. Now the right calls are
in place.

We changed the error style, so they're all wrong. Now they're right.
😄