Add test:all and test:all:db rake tests to speed up full test runs.

Improve img alt attribute for screen readers

fix a typo on the engine guide

Supress warning about method redifinition

In i18n gem, the following methods are defined.
- `Hash#except`
- `Hash#slice`

But if there are defined already, i18n skips these definitions.
So these definition by `active_support` are required before `require 'i18n'`.

Update to latest Unicode data.

Remove method redefined warning

In `i18n` gem, the method definition of  `Hash#deep_merge!` is skipped
when it is already defined.

- warning: method redefined; discarding old deep_merge!

Release notes at: http://www.unicode.org/versions/Unicode6.2.0/

added compress options for gzip

added test for compress options of gzip

update changelog

Currently, the img_alt method in ActionView keeps underscores
in the alt attribute. Because underscores are pronounced in
Apple's VoiceOver Utility, this has serious implications for
accessibility. This patch makes underscored or hyphenated file
names (both common in projects) read more naturally in screen
readers by replacing them with spaces. See method documentation
for details.

Added documentation to image_alt method

The `:controller` option for routes can contain numbers. closes #9231.

Added notice message for destroy method in scaffold

Use IN operator like Arel for empty hash in where clause

Fix #9168 Initialize NullCookieJar with all options needed for KeyGenerator

Describe better the changes related to raising errors with empty
array/hash values in where clauses.

[ci skip]

Activer Record:  Change behaviour with empty array in where clause

Active Record: Change behaviour with empty hash in where clause

Fix article for generator name

active_record: Quote numeric values compared to string columns.

Travis failed because the postgresql version installed there does not
support extensions, so we just need to skip this for now.

There is no need to create the extension in the database just to test if
it's dumped, we can stub that instead.

When extensions are supported but there's no one enabled in the
database, we should not print anything related to them in schema.rb.