[ci skip] Mention the change in nil handling for serialized attributes
in "Upgrading from Rails 3.2 to Rails 4.0"
[ci skip] Clarify the "Serialized Attributes" section

Mention that the change in nil handling for serialized attributes
affects custom coders.
Allow password to contain spaces only.
[ci skip] Updated create! documentation description and added +attributes+ for rdoc
Remove ActionController::RaiseActionExceptions.

The latest modification to the code was done in https://github.com/rails/rails/commit/5e3517ea. In Rails 3.2,
`ActionController#rescue_action` was deprecated and `rescue_action_without_handler` is no longer being used.
Merge pull request #16419 from tgxworld/remove_legacy_code

Remove ActionController::RaiseActionExceptions.
Merge pull request #16412 from yevhene/master

Fix in has_secure_password for passwords containing only spaces.
Fix typo [ci skip]
Tables existence check query is executed in large quantities

When Rails starts, tables existence check query is executed
number of models.
In case of mysql,

    SHOW TABLES LIKE 'table1';
    SHOW TABLES LIKE 'table2';
    SHOW TABLES LIKE 'table3';
    ...
    SHOW TABLES LIKE 'table999';

Add process to get the names of all tables by one query.
Fix spelling.
Merge pull request #16422 from tgxworld/fix_spelling

Closes #16422
change to empty? from blank?
Merge pull request #16421 from tsukasaoishi/prevant_manycall_showtables

Tables existence check query is executed in large quantities
use the uri parser so that newer version of Ruby work
remove dead file_watcher code
Merge pull request #16424 from gregors/remove_dead_code

remove dead file_watcher code
defer running after_config hooks until after the object is allocated
add a new constructor that runs load hooks
need to call super
Stop using padding in the generated Gemfile -- it looks shit