Use Ruby on Rails Coding Conventions for code examples in the guides

* Indent after private/protected
* Ruby >= 1.9 syntax for hashes
* Prefer method { do_stuff } instead of method{do_stuff} for single-line blocks.

[ci skip]
hm:t join tables may not have a primary key
Merge pull request #12155 from jetthoughts/reformat_guides_code_examples

Use Ruby on Rails Coding Conventions for code examples in the guides
Use MiniTest::Unit::TestCase instead of Minitest::Test

Since Rails 4.0.x is depending on Minitest 4.x, the constant won't be
available so the gist won't run.

[ci skip]
Fix fixtures regression that required table names to map to classes only, not class names
Typo in Changelog.
Merge pull request #12164 from rywall/patch-1

Typo in Changelog. [ci skip]
[ci skip] Change link name of Rails i18n wiki.

Actually it's Ruby i18n link.
Merge pull request #12166 from JuanitoFatas/doc-patch-1

[ci skip] Change link name of Rails i18n wiki.
Improves a sentence in guides/security

Changed "... books make this wrong" to "... books get this wrong"
Merge pull request #12157 from robin850/patch-9

Use MiniTest::Unit::TestCase instead of Minitest::Test  [ci skip]
Fixed API task file

1. As we have vendor in AV only
2. No more vendor in AC
3. No vendor folder in AR
grab executable from rubygems
Fix order dependent test

see c48cbb02d7e6f585e31b404c0c363f0d6b586811
Back AV description in gemspec
Merge pull request #12167 from hannesfostie/grammar-improvement

[ci skip] Improves a sentence in guides/security
Remove BasicRendering and remove template functionality from AbsC::Rendering
Remove remaining coupling with AV in MimeResponds
Remove BasicRendering tests
Remove helper fixtures not used in any test

The fixture for module AbcHelper defines three functions bare_a,
bare_b and bare_c, but only bare_a is used in the code that tests
helper functions.