fix typo in the credit section of the guides. [ci skip]
Soften wording about knowing other devs.

Many people don't, so point them to a place where they can meet
some.
Flesh out feedback portion of contributing guide.

I don't know of anyone that hangs out in #rails-contrib, and we should
also let people know that feedback can take some time.
Add note about features vs. bugs.

Sometimes people ask what makes a feature and what makes a bug, so
let's clarify that so we can show it to people later.
Warning on doc for assets under lib|vendor not precompiling [ci skip]
Merge pull request #12037 from SamSaffron/mem_alloc

Performance: Reduce memory allocations in Active Record
Review Action Mailer CHANGELONG

[ci skip]
Merge pull request #12038 from SamSaffron/memoize_decorate_cols

Perf: memoize serialized column list and time zone column list
Ensure all-caps nested consts marked as autoloaded

Previously, an autoloaded constant `HTML::SomeClass` would not be marked
as autoloaded by AS::Dependencies. This is because the
`#loadable_constants_for_path` method uses `String#camelize` on the
inferred file path, which in turn means that, unless otherwise directed,
AS::Dependencies watches for loaded constants in the `Html` namespace.

By passing the original qualified constant name to `#load_or_require`,
this inference step is avoided, and the new constant is picked up in the
correct namespace.

Conflicts:
	activesupport/CHANGELOG.md
Merge pull request #12015 from vipulnsward/add_dynamic_finders_to_upgrade

Add Finder API changes to upgrading guide [ci skip]
Merge pull request #11805 from jetthoughts/11803_update_move_forbidden_exception_description_before_show

[Getting Started Guide] Move Forbidden attributes description before show post section [ci skip]
Conflicts:
	guides/source/getting_started.md
Merge pull request #11768 from cloudspace/cache_template_loading

Only cache template digests if !config.cache_template_loading
Conflicts:
	actionview/CHANGELOG.md
Merge pull request #12048 from tjouan/app_generator-bin_perms-umask

Comply with current umask when generating new app
Merge pull request #10642 from LTe/invalid-load-error

Show real LoadError on helpers require
Conflicts:
	actionpack/CHANGELOG.md

Closes #12055.
Merge pull request #12076 from dabit/master

Fix broken link to Fixtures documentation on guides and activerecord tests [ci skip]
Merge pull request #12085 from valk/master

FIX reload! within rails console --sandbox causes undefined method rollb...
Make AR::Base#touch fire the after_commit and after_rollback callbacks