Revert "correct css selector for the display of validation error messages: changed #error_explanation to #errorExplanation"

At least in master the selector is snake case.

This reverts commit ba2fed41613e02bb6cfc46c92ace00abb99ce313.
Use assert_nil instead of assert_equal
Add comment to a table without model.

This table is being used to verify if the :limit options is being
ignored for text and binary columns
Fix some indentation in the postgresql_specific_schema
Revert "rails gem has no lib directory to require"

This reverts commit 6bcbd6046f82c5f0114249a6b725f9679a140b9a.

The default value for require_paths is ['lib'], and Rails does not
need to include any lib/ file to build the gem, so the previous
commit 'makes sense'. However, gems will not be built at all if
require_paths is empty (see https://gist.github.com/1065473), so
it's better to stick with the default, which does not have any
side-effects
Merge pull request #8350 from claudiob/restore_default_require_paths

Revert "rails gem has no lib directory to require"
Specify type of singular association during serialization

When serialising a class, specify the type of any singular associations, if
necessary. Rails already correctly specifies the :type of any enumerable
association (e.g. a has_many association), but made no attempt to do so for
non-enumerables (e.g. a has_one association).
We must specify the :type of any STI association. A has_one
association to a class which uses single-table inheritance is an example of
this type of association.

Fixes #7471
Merge pull request #8352 from steveklabnik/update_7858

Specify type of singular assication during serialization
Ensure that associations have a symbol argument.

Fixes #7418.
Merge pull request #8355 from steveklabnik/update_7418

Ensure that associations have a symbol argument.
Fix documentation for String#mb_chars.

This documentation has been out of date.
Simplify String#mb_chars and stop proxying #class

This behavior mattered under Ruby 1.8, but that doesn't matter now
that we don't support it.

In addition, we don't want to proxy the #class method. A test was added
to prevent against regressions.
Merge pull request #8261 from steveklabnik/fix_mb_chars

Simplify String#mb_chars and fix documentation.
Remove observers and sweepers

They was extracted from a plugin.

See https://github.com/rails/rails-observers

[Rafael Mendonça França + Steve Klabnik]
Gracefully handle upgrading apps with observers

Rather than just raising a NoMethodError when copying the config, this
commit adds a warning message until either the rails-observers gem is
installed or the relevant config options are removed.
Merge branch 'extract_observers'
Fix typo in the Observers deprecation message. [ci skip]
Merge pull request #8361 from lucasmazza/typo

Fix typo in the Observers deprecation message.
added examples when options is string
Add CHANGELOG entries for the observes extraction

[ci skip]