Locate `=require turbolinks` at the bottom of application.js

Turbolinks should be located at the bottom of application.js
to detect assets change properly.

Ensure original encoding does not change in mb_chars test.

See https://github.com/ruby/ruby/commit/9c1b3161f20162dc1682d758c0e4d2fc3a74745e

All Active Support tests pass in 2.0.0preview2 after this change.
Closes #8409

Override <%== to always behave as literal text rather than toggling based on whether escaping is enabled. Fixes that existing plaintext email templates using <%== unexpectedly flipped to *escaping* HTML when #8235 was merged.

Fix wrong doc and message about rails profiler.

Related to changes introduced in 553b5637

Updates to the Migration Guide

More descriptive error when rendering a partial with `:layout => true`

Add db to the list of default annotation folders

ActiveModel::Errors spec fixes

Quote ~ in git config global excludes command.

This will put ~/ in .gitconfig so it will not be hardcoded to the home
directory where the command was run.

When there are missing components in the Hash returned by
Date._parse only the date components should default to the
value of Time.zone.now, the time components should all
default to zero.

Add Mailer Callback section to Mailer guides

Reset attributes should not report changes.

When resetting an attribute, you expect it to return to the state it was
before any changes. Namely, this fixes this unexpected behavior:

~~~ruby
model.name = "Bob"
model.reset_name!
model.name_changed? #=> true
~~~

This introduces a bunch of editing/re-writing to the migrations guide.
There were a bunch of small changes, and a few larger ones:

* mysql does support transactions.
* Add a section about db/seeds.rb
* Largely re-wrote the first few sections

Validations guide

plus:

* 80 column formats
* replacing the explanation of the dynamic_form gem with the example
  HTML/CSS that Rails scaffolds generate.

Conflicts:
	guides/source/active_record_validations.md

Fix #8167 - adding autoloading support for caching

Patched Marshal#load to work with constant autoloading (active_support/dependecies.rb) (issue #8167)

Chrome, Safari and Firefox serialize Date objects to strings such
as 'Mon May 28 2012 00:00:00 GMT-0700 (PDT)'. When these strings
are parsed the zone is interpreted as 'GMT-0700' which doesn't
exist in the TzInfo list of timezones.

By taking advantage of the improved date/time handling in 1.9.3
we can use `Date._parse` and the `:offset` value which is parsed
correctly.

Three tests were amended to make them pass:

1.  test_parse_with_old_date

    This needed changing to a different value because the original
    value was before EST was adopted so was being changed to a
    LMT (Local Mean Time) value after the change. It didn't before
    because `DateTime` just has offsets from UTC not timezones.

2.  test_parse_should_not_black_out_system_timezone_dst_jump

    Changed the implementation of this test as the stubs were
    dependent on internal implementation details of the test.
    Confirmed that the modified test still failed when the
    implementation of `parse` was restored to pre-#5571.

3.  test_parse_should_black_out_app_timezone_dst_jump

    Ditto.

Closes #5770.

Remove references to AR::Observer from docs

ActiveRecord::Observer was extracted into a separate gem so it
should not be referenced anymore (see https://github.com/rails/rails/commit/ccecab3)