The following constants were renamed:

  ActiveModel::Serialization     => ActiveModel::Serializable
  ActiveModel::Serializers::JSON => ActiveModel::Serializable::JSON
  ActiveModel::Serializers::Xml  => ActiveModel::Serializable::XML

The main motivation for such a change is that `ActiveModel::Serializers::JSON`
was not actually a serializer, but a module that when included allows the target to be serializable to JSON.

With such changes, we were able to clean up the namespace to add true serializers as the ArraySerializer.

Issues/3737 AS::Cache.expand_cache_key

Fix #3728 Remove unreachable code, and add additional testcases.

`nil` and `false` both expand to `""` (empty string), while `true` expands to
`"true"`; `false` should expand to `"false"`

`cache_key` method is never called when the argument is a 1-element array
with something that responds to `cache_key`

Fix inconsistencies with Time{WithZone}#{hash,eql?}

stylesheet_tag default's media is "screen"

javascript_include_tag should add '.js' to sources that contain '.'

Show exceptions refactor: controller should be responsible for choice to show exceptions

tests predicates according to the boolean interpretation of their return value, not expecting specifically true or false

Respecting Genuine assert_equal false Edition

This avoids the unnecessary "yo dawg, I heard you like include, so I put a module that includes your module when it is included" approach when building extensions.

Revert "tests predicates according to the boolean interpretation of their return value, not expecting specifically true or false"

Reason: there were some genuine tests for false when
reading values, going to revise those ones.

This reverts commit a539a5e3.

tests predicates according to the boolean interpretation of their return value, not expecting specifically true or false

This is done since the -h option to dbconsole hides the conventional
-h for help and forces users to use --help to see the usage options for
dbconsole.

Bump Arel

This reverts commit 3178cc9a.