docs: Replace an unpleasant grammatical construct.

[ci skip]

Add Application#message_verifier method to return a message verifier

It is an application global verifier that can be used to generate and
verify signed messages.

See the documentation of ActiveSupport::MessageVerifier for more
information.

Escalate missing error when :raise is true in translate helper, fix regression introduced by security fix.

Before ec16ba75,
ActionView::Helpers::TranslationHelper#translate has raised errors with
specifying options[:raise] to true.

This should work by this fix:

     begin
       t(:"translations.missing", raise: true)
     rescue I18n::MissingTranslationData
       p :hello!
     end

update guides to new version of rails 3.2.x [ci skip]

Fixed json_escape (again)

Expanded test coverage for html_escape and json_escape

removed duplicate test case

remove nil in NullType#ref.

Return Nil is implicit in a method and this syntax is used in the others
classes

Formatting, capitalization, and punctuation fixes [ci skip]

Second try on this commit.