Set Psych as the YAML engine for Rubinius

Since the rubysl-yaml gem doesn't ship with Psych by default because of
its dependency on libyaml, on Rubinius, the default engine is Syck.

However, if we want to be able to run the application safely on
different rubies, we need to make people using Rubinius rely on Psych.

See http://git.io/uuLVag for further information.
Do not set enforce_available_locales to i18n 0.7

Now the default is always true.

Users still can set it using config.i18n.enforce_available_locales.
Merge pull request #16267 from robin850/rbx-yaml

Set Psych as the YAML engine for Rubinius
Dev and edge application and plugins need to include i18n master
Fix syntax error
Remove mocha usage
Calling require_self twice in css raises Sprockets::ArgumentError exception [ci skip]
Merge pull request #16260 from akshay-vishnoi/doc-change

Calling require_self twice in css raises Sprockets::ArgumentError exception [ci skip]
[ci skip]Add i18n master to the Gemfile
Merge pull request #16276 from y-yagi/bug_report_templates

[ci skip]Add i18n master to the Gemfile
pg, `change_column_default, :table, :column, nil` issues `DROP DEFAULT`.

Closes #16261.

[Matthew Draper, Yves Senn]

Using `DEFAULT NULL` results in the same behavior as `DROP DEFAULT`.
However, PostgreSQL will cast the default to the columns type,
which leaves us with a default like "default NULL::character varying".

/cc @matthewd
Fixes #16265
Fix documentation typo in ConnectionSpecification::Resolve.spec
Merge pull request #16280 from a3gis/master

Fixes #16265 and correct documentation typo
clenaup, unify CHANGELOG format. [ci skip]
fix, mysql `db:purge` respects `Rails.env`.

Previously this method always established a connection to the test database.
This resulted in buggy behavior when combined with other tasks like
`bin/rake db:schema:load`.

This was one of the reasons why #15394 (22e9a91189af2c4e6217a888e77f22a23d3247d1)
was reverted:

> I’ve replicated it on a new app by the following commands: 1) rails
  generate model post:title, 2) rake db:migrate, 3) rake
  db:schema:load, 4) rails runner ‘puts Post.first’. The last command
  goes boom. Problem is that rake db:schema:load wipes the database,
  and then doesn’t actually restore it. This is all on MySQL. There’s
  no problem with SQLite.

  -- DHH

https://github.com/rails/rails/commit/22e9a91189af2c4e6217a888e77f22a23d3247d1#commitcomment-6834245
build fix, fix error introduced with 091b246bb0111357edbb9703ea342a944b04deb6

Fixes the following issue:

  1) Failure:
ActiveRecord::MySQLPurgeTest#test_establishes_connection_to_test_database [test/cases/tasks/mysql_rake_test.rb:200]:
not all expectations were satisfied
unsatisfied expectations:
- expected exactly once, not yet invoked: ActiveRecord::Base.establish_connection(:test)
satisfied expectations:
- allowed any number of times, invoked once: #<Mock:0x2349430>.recreate_database(any_parameters)
- allowed any number of times, invoked once: ActiveRecord::Base.establish_connection(any_parameters)
- allowed any number of times, invoked once: ActiveRecord::Base.connection(any_parameters)
tests, run adapter specific rake tests only for the right adapter.
Make HWIA copy the default proc too.

[fixes #16279]
Merge pull request #16281 from arthurnn/copy_default_proc_hwia

Make HWIA copy the default proc too.