Change links to 37signals and svn blog to point to new destinations. [ci skip]

Includes https://github.com/rails/rails/pull/14711 and some cleanup
commits.

Fixes #13648

Activerecord fix aggregate methods with select

Improve debugging support

Move assets precompile (and version) to an initializer

Enhance routing error html page

Be explicit about allowed constraint values, fixes #14702

PostgreSQL automatic type map reload

sprockets-rails 2.1 needs the precompile list to be available in all
environments.

Add more test case for #demodulize, Improve documentation

Tested on a brand new app to exactly match current byebug's behaviour.

Add a failing test for a URL helper that was broken by a6b9ea2e.

Since `:shallow` may be set at any point in the resource nesting we should
only make the new and collection routes shallow when the parent is shallow.

This is a bit of a hack but until the mapper is refactored to an object graph
instead of a hash of merged values it's the best we can do.

Fixes #14684.

- also refactored the javascript.

[Yves Senn & Matthew Draper]

[Yves Senn & Matthew Draper]

[ci skip]

The examples are written in a way you expect them to be executable.
However one snippet assumed there to be two comments when only one
was created above.

The defined models did not extend `ActiveRecord::Base`

The example used `comments.last.mark_for_destruction`. This does no
longer load the whole collection but just the last record. It is
then refetcht on subsequent calls to `last`. This breaks the example.

Fix insertion of records for hmt association with scope

Conflicts:
	activerecord/CHANGELOG.md

Add after_commit/after_rollback to callback list

[ci skip] Remove false documentation

Adding after_commit/after_rollback to list of callbacks in order helps
explain the callback order as well as making it consistent with the API
docs at http://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html