modified:   guides/source/getting_started.md

The option backed to `start` in da269343.

- This change is made as the behavior for `:message` proc was changed in
  https://github.com/rails/rails/pull/24119.
- Also check
  https://github.com/rails/rails/pull/24431#issuecomment-206106790 for
  reference.

- Update info for weak ETag
- Add info for strong ETag
- Add examples for strong and weak ETags
- Display difference between generated strong and weak ETags strings.

Fix Active Model basics introduction to indicate it only introduces us to integration and not complete i18n framework.

[ci skip]

 [ci skip]

- Removed entry for # Template Collection from release notes.
- Remove duplicate entry for caching Action mailer views.
- Remove duplicate entry for left_outer_joins.

`datetime_field` was deprecated in 316811b4

[ci skip]

Passing `true` to the association has been deprecated.

Add `:other_than` option documentation.

[restful-authentication](https://rubygems.org/gems/restful-authentication/versions/1.2.1) hasn't been updated since 
September 6th, 2012 so it might not be a great idea to recommend that Rails users try it out.

Devise seems like a much more popular and secure solution that automatically resets sessions on sign in and out 
so it's a great example in this case. 

/cc @tenderlove @josevalim

s/symantically/semantically/

[ci skip]

[ci skip]

[ci skip]

Sync AV, AR, AJ, AS, AM changelogs with our 5.0 release notes draft.
This is a follow up to c94045dc and contains changes made since the
release of beta1.

[ci skip]

This updates the 5.0 release notes guide to reflect changes that
happened after beta1 has been released.

I'll sync the other changelogs later today but I'll push this batch to
prevent against cumbersome merge conflicts.

Follow up to 625baa69

The logger interface to get all Rails features is not obvious. This change adds documentation on how to assign a logger that will use all Rails features.

We are also matching the stdout logging interface to the default logger in bootstrap https://github.com/rails/rails/blob/f5a5988352b165143f0f9d622707c351c1470882/railties/lib/rails/application/bootstrap.rb#L42-L45.

In this patch, all log-related stuff in `ActiveSupport::Dependencies`
is removed because the logging is no longer useful.

Follow up to #24115.

Clarifies the documentation here to mean all options are for when the
relation is destroyed; also now reflects the documentation on this same
option found in the has_one section.