cc https://github.com/rails/rails/issues/14848#issuecomment-41198795

jQuery, SQLite3 and Unicorn use these respective capitalizations pretty much everywhere else in the comment sections of the project.

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Closes #15141.

This version fixes an API breakage between 3.0 and 3.1 ; the header
method's arity should not have changed.

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This is no longer true as @jeremy removed the deprecation in 7a5601c4.

Updated CHANGELOG.md with entry about :host in asset_url

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Also change Json => JSON.

Fill Ruby's Range & IPAddr link.

Previously, only the object and method name from the label tag were
used when looking up the translation for a label. If a value is
given for the label, this ought to be additionally used. The
following:

    # form.html.erb
    <%= form_for @post do |f| %>
      <%= f.label :type, value: "long" %>
    <% end %>

    # en.yml
    en:
      activerecord:
        attributes:
          post/long: "Long-form Post"

Used to simply return "long", but now it will return "Long-form
Post".

* Strips leading underscores.
* Changes some unnecessary gsub!s to sub!s.
* Replaces some anchors ^, $ with \A, \z.
* Documents that human inflection rules are applied.
* Documents that words are downcased except acronyms.
* Adds an example with an acronym.
* Rewords docs.

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on the Getting Started guide.

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Added 2 changes suggested by @robin850 [skip ci]

Let's tell people that they should rely on Tokaido instead of Rails One
Click.

Fixes #14960.

This reverts commit fe985960, reversing
changes made to add95606.

Benefits: https://creativecommons.org/version4

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.

[ci skip]

Update the Getting Started tutorial to clarify where and how to add
controller actions, and fix some grammar.

This PR is an improved version of #14828, #14822 and #14815.

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