Merge branch 'action-mailer-async-doc-fixes' of https://github.com/mfazekas/rails into mfazekas-action-mailer-async-doc-fixes

Conflicts:
	actionmailer/lib/action_mailer/base.rb

Error message no longer tells you to set the (deprecated) secret_token.

[ci skip] Update contributing guide

remove reference to `register_javascript_expansion` and `register_stylesheet_expansion` from guide [ci skip]

remove reference to `register_javascript_expansion` and `register_stylesheet_expansion` from guide [ci skip]

These methods no longer exists.

Speed up Levenshtein by 50% and reduce 97% of memory usage

  Calculating -------------------------------------
             each_char   924.000  i/100ms
        each_codepoint     1.381k i/100ms
  -------------------------------------------------
             each_char      9.320k (¡Þ 5.1%) i/s -     47.124k
        each_codepoint     13.857k (¡Þ 3.6%) i/s -     70.431k

  Comparison:
        each_codepoint:    13857.4 i/s
             each_char:     9319.5 i/s - 1.49x slower

The full report can be found here:
  https://gist.github.com/yuki24/a80988f35aceac76f1d5

[ci skip] remove duplicate doc for current_page?

It was removed long ago: e358b1fc.

Missing note on validates_presence_of validation [ci skip]

Without this note, someone can misunderstand the usage of validates_presence_of method

add missing note for the validates_presence_of

Rename railties/bin to railties/exe to match the new Bundler convention

That will match the new Bundler executables convention.
Bundler Blog Post: http://bundler.io/blog/2015/03/20/moving-bins-to-exe.html
Also updated the necessary tests.

fix a wrong feature test method name

These methods were removed in cb9f7f48 and are no longer methods in the
Rails codebase.

[skip ci] primay_key -> primary_key

Merge branch 'belongs_to_primary_key_doc' of https://github.com/girishso/rails into girishso-belongs_to_primary_key_doc

[docs] Using the real resolver pattern in docs

Merge branch 'queue-adapters-docs' of https://github.com/KingsleyKelly/rails into queue-adapter-docs

Use `use_transactional_tests` in Active Record

`use_transactional_fixtures` was deprecated in favor of
`use_transactional_tests` in Rails 5.0. This removes one warning while
running test suite.

[ci skip] Downcases filter names

[Rails4 regression] prevent thin and puma cause error in Non ASCII URL
on Windows

* https://github.com/rails/rails/issues/19187
* https://github.com/rails/rails/pull/19533
* https://github.com/macournoyer/thin/issues/268

These are serious Rails 4 regression for Redmine Bitnami Windows users.

https://community.bitnami.com/t/problems-with-3-0-1-installation-see-report-inside/30195/

It is not caused on webrick users.

Related:

* https://github.com/rack/rack/issues/732#issuecomment-67677272
* https://github.com/phusion/passenger/issues/1328

Related: #19617, #19187, #19533, #19689, #19675.

'drb/unix' does not exist on mingw.

Related: #19617, #19187, #19533, #19689, #19675.

This is POC (Proof Of Concept) which bundler does not remove mingw lines.
https://github.com/rails/rails/pull/19617#issuecomment-90293795