Rubinius has problems with bundling when shared gems are disabled (ie.
when --path or --deployhment is used). There is no real reason to
install it with --path on TravisCI, so I'm dropping it.

The contract of blank? and present? was in principle to return Object, as we
generally do, the test suite and description was consistent with that, but some
examples had comments like "# => true".

This cannot be unclear, we either fix the examples, or update the contract.

Since users may be already assuming singletons due to the examples and the fact
that they were returned before 30ba7ee5, the safest option seems to be to revise
the contract and the implementation of String#blank?

The motivation for 30ba7ee5 was to improve the performance of the predicate, the
refactor based on === is on par regarding speed.

With this commit we start documenting return types using YARD conventions. We
plan to document return types gradually.

String#blank? returns True/False

Removed warnings: setting `changed_attributes` instance variable if it is already initialized.

Typo fix [ci skip]

Copy changed_attributes across to newly become'd records

6.3.0 was released on September 30, 2013.

http://unicode-inc.blogspot.com.ar/2013/09/announcing-unicode-standard-version-63.html

Without this, the original record's values won't get saved, since the partial insertions support (https://github.com/rails/rails/commit/144e8691cbfb8bba77f18cfe68d5e7fd48887f5e) checks for changed values and thinks there are none.

Ensure backward compatibility between Minitest 5 and 4

Define Minitest::Test in case we are running the gist under Minitest 4
and avoid relying on MiniTest::Unit::TestCase to avoid displaying
warning on version five.

[ci skip]

Adding missing backslashes in active_model files so as to avoid unwanted [ci skip]

rbconfig is not used in these files remove unused requires

Minitest::Unit::TestCase is Minitest::Test [ci skip]

remove unused requires

Use String#scrub when available to tidy bytes

Fixed typo in Rails 4.1 Release Notes [CI skip]

Improve font of some code in API documentation [ci skip]

* Add "<tt>" or "+" to improve font of some code and filenames in API documentation
* Does not contain wording changes

Updated documentation for Attribute Methods [ci skip]

Partial fix of database url tests

Right now `db:drop` depends on `load_config` since so when `db:drop` gets executed `load_config` gets run. `db:structure:load` depends on `[:environment, :load_config]`. So before it runs, it executes `environment` but because `load_config` has already executed it is skipped. Note `db:load_config` is "invoke"-d twice, but only "execute"-d once:

```
** Invoke db:drop (first_time)
** Invoke db:load_config (first_time)
** Execute db:load_config
** Execute db:drop
** Invoke db:structure:load (first_time)
** Invoke environment (first_time)
** Execute environment
** Invoke db:load_config
** Execute db:structure:load
```

The fix for this is making sure that the environment is run before any `load_config`:

```
** Invoke environment (first_time)
** Execute environment
** Invoke db:drop (first_time)
** Invoke db:load_config (first_time)
** Execute db:load_config
** Execute db:drop
** Invoke db:structure:load (first_time)
** Invoke environment
** Invoke db:load_config
** Execute db:structure:load
```

Prior to #13463 when `DATABASE_URL` was set, Rails automagically used that value instead of the database.yml. There are tests in dbs_test that expect this to still be true. After that PR, `RAILS_DATABASE_URL` is expected to be read into the YAML file via ERB, this PR fixes that behavior.

Note: this does not entirely fix the tests. It seems that `ActiveRecord::Tasks::DatabaseTasks.current_config` does not process the url string correctly (convert it into a hash), and ` ActiveRecord::Tasks::DatabaseTasks.structure_load(current_config, filename)` as well as other methods in `DatabaseTasks` expect a hash.

It seems like we should involve the resolver somewhere in this process to correctly convert the database url, I do not know the best place for that /cc @josevalim

Fix railties warnings

Warning:

  DEPRECATION WARNING: Passing a string to ActiveRecord::Base.establish_connection for a configuration lookup is deprecated, please pass a symbol (:development) instead.

Warning:

  ~/projects/rails/activerecord/lib/active_record/railtie.rb:140: warning: method redefined; discarding old extend_message
  ~/projects/rails/activerecord/lib/active_record/errors.rb:104: warning: previous definition of extend_message was here

Move mysql2 test for when adapter will be loaded