Introduce `ActionView::Template::Handlers::ERB.escape_whitelist`.
This is a list of mime types where template text is not html escaped
by default. It prevents `Jack & Joe` from rendering as
`Jack &amp; Joe` for the whitelisted mime types. The default whitelist
contains text/plain.

This follows a whitelist approach where plain text templates are
not escaped, and all the others (json, xml) are. The mime type is
assumed to be set by the abstract controller.
Use Integer#div instead of Integer#/ to avoid side effects from mathn
Merge pull request #8235 from tilsammans/dont_escape_actionmailer_when_plaintext

Introduce `ActionView::Template::Handlers::ERB.escape_whitelist`
Simplify (and optimize)
Merge pull request #8236 from marcandre/use_div

Use div
Switch to 1.9 hash syntax & remove some parentheses when it reads nicer
Add a consideration note

regarding linking to Kindle
Switch to 1.9 hash syntax
Switch to 1.9 hash syntax
Switch to 1.9 hash syntax (guides)
Switch to 1.9 hash syntax (guides)
Remove unnecessary whitespace
Add link to the Application Templates guide
Remove unnecessary whitespace
Fix failing template tests

Introduced in 4a4de567b45ff28035419bc2d92f9b206e3c0a66.
Refactor url methods a bit

Use if..else conditions instead of return guards.
Use _ for not used arguments when iterating.
Set the path variable directly instead of using an empty string and <<.
Remove config.threadsafe! from production env template

Closes #8232 [ci skip]
Move changelog entry from #8235 to the top [ci skip]
Update the middleware stack to reflect the current Rails output

Specifically, remove `ActionDispatch::Head` in favor of `Rack::Head`.
Depend bundler from `=> 1.2.2` to `< 2.0`