Fix PostgreSQL TIMESTAMP WITH TIME ZONE to return ActiveSupport::Time

In an AR model a timestamptz attribute would return a ruby string and AR
tests did not check for any type casting.  Previous tests would pass
only because an assert_equal was being used on a Time.utc object, which
will parse the right side of the eq to a valid Time instance for
comparision.

switch to test instance of Time instead of ActiveSupport::TimeWithZone
New beauty pages(404, 422, 500)

moving changelog note to unreleased section

New beauty pages(404, 422, 500)
:scissors: extra blank line
Merge pull request #9431 from troyk/patch-2

Fix PostgreSQL TIMESTAMP WITH TIME ZONE to return ActiveSupport::Time
Remove hard coded references to Active Record in railties
Merge pull request #9512 from Jacke/master

New 404, 422, 500 pages, they are more stylish and bring ruby essence…
integrate the strong params README into the AC guide.

The current ActionController guide does not mention strong parameters
at all. I integrated the README into the guide to explain the API.

I also included a section to illustrate that the API does not solve
all possible whitelisting scenarios.

The origin was #9454.
Merge pull request #9465 from senny/document_strong_params_in_ac_guide

integrate the strong params README into the AC guide.
Use custom visitor class for optimized url helpers

Rather than trying to use gsub to remove the optional route segments,
which will fail with nested optional segments, use a custom visitor
class that returns a empty string for group nodes.

Closes #9524
Bring config.allow_concurrency back

Since the Rack::Lock still exists in development,
let's provide a way to disable it explicitly.