Log Message:
Import ruby-railties-4.2.8 as devel/ruby-railties42

Notable changes since 3.2:

- New test locations test/models, test/helpers, test/controllers, and
  test/mailers. Corresponding rake tasks added as well.
- Your app's executables now live in the bin/ directory. Run rake
  rails:update:bin to get bin/bundle, bin/rails, and bin/rake.
- Threadsafe on by default
- Ability to use a custom builder by passing --builder (or -b) to
  rails new has been removed. Consider using application templates
  instead.
- The Spring application preloader is now installed by default for new
  applications. It uses the development group of the Gemfile, so will
  not be installed in production.
- BACKTRACE environment variable to show unfiltered backtraces for
  test failures.
- Exposed MiddlewareStack#unshift to environment configuration.
- Added Application#message_verifier method to return a message
  verifier.
- The test_help.rb file which is required by the default generated
  test helper will automatically keep your test database up-to-date
  with db/schema.rb (or db/structure.sql). It raises an error if
  reloading the schema does not resolve all pending migrations. Opt
  out with config.active_record.maintain_test_schema = false.
- Introduce Rails.gem_version as a convenience method to return
  Gem::Version.new(Rails.version), suggesting a more reliable way to
  perform version comparison.
- Introduced web-console in the default application Gemfile.
- Added a required option to the model generator for associations.
- Introduced the x namespace for defining custom configuration options.
- Introduced Rails::Application.config_for to load a configuration for
  the current environment.
- Introduced a --skip-turbolinks option in the app generator to not
  generate turbolinks integration.
- Introduced a bin/setup script as a convention for automated setup
  code when bootstrapping an application.
- Changed the default value for config.assets.digest to true in
  development.
- Introduced an API to register new extensions for rake notes.
- Introduced an after_bundle callback for use in Rails templates.
- Introduced Rails.gem_version as a convenience method to return
  Gem::Version.new(Rails.version).