Fix spacing issue
4.0 Release notes should point to 4.0 Changelog
Be assertive about adding `[ci skip]` message
`attibutes` => `attributes`
`implemention` => `implementation`
Example of Join models

In the example of join models, there are five models but in the explanation only consider Category, Post, Comment and Guest.
Client.exists?(1,2,3) and Client.exists?([1,2,3]) does not work

The right command for doing that is Client.exists?id:[1,2,3]
Exists does not work like find method, in find method you can do Person.find(1, 2, 6) or Person.find([7, 17]) but not Person.exists?(1,2,3) or Person.exists?([1,2,3])
Review the changes made on 90155b4e28a3887dce9428e9df150ede3d6c7465
added # or comment
Cleanup of excerpt helper

* replaced String concatenation by joining
* separator has default value to '', even it is nil
do not break params filtering on nil values

closes #12149
Allow Relation#from to accept other relations with bind values.
Blacklist refferenced in docs is actually whitelist
The docs refference a blacklist, but really what's being described
is a whitelist. Anything that matches the constraint gets through to
the path.
Change documentation to consistently refer to the same object
The documentation in this section is referring to a profile,
so the resource that's created should probably also be a
profile of some sort.
form_for - fix :namespace and :as options clash

:as option should not overwrite :namespace option when
generating html id attribute of the form element. id should be prefixed
by specified namespace even if :as option is present

Add test case showing the issue and code fixing it
html generated for a search form

There's a div that is generated in rails for a default search form and is not includen in the example.
[ci skip] Add missing setting locale code snippet.

This is for 3 Internationalizing your Application of i18n.md.

Missing the code as mentioned in 2.3, setting locale.

Without this, the example to add config/locales/pirate.yml will not work.
[ci skip] Fix links in section 5.3 of i18n.md

Now all links point to the correct line number.
[ci skip] Documentation on how to create custom rake tasks.
Plural of Deer not deer

Change the plural of Deer word in the naming conventions