ActionController::Live documentation in the guides.

I'm adding documentation to the action_controller_overview guide which
should tell people how to stream arbitrary data.
it's xml, not json

change docs for xml serializer to talk about xml
Merge pull request #11427 from jmondo/patch-1

it's xml, not json
Merge pull request #11426 from wangjohn/action_controller_live_docs

ActionController::Live documentation in the guides.
[ci-skip] Update link, tweak UglifyJS
Merge pull request #11428 from evangoer/minor_asset_pipeline_docfix

Update YUI Compressor link; tweak UglifyJS
This is not needed anymore, before_initialize block can access config
Merge pull request #11424 from kennyj/fix_column_defaults_caching

Reset @column_defaults when assigning locking_column.
Added actionview in API generation [ci skip]

CHANGELOG and LICENSE removed as suggested
memorized -> memoized typo fix [ci skip]

Reverts one line from 457b7ff9
Merge pull request #11431 from ianfleeton/initialization_memoized_typo

memorized -> memoized typo fix [ci skip]
Merge pull request #11425 from arunagw/actionview_api_generation

Actionview api generation
Removed unused broken task for update README [ci skip]
Removed unused require from Rakefile
Merge pull request #11433 from arunagw/removed_unused_task

railties Rakefile tweaks
Fix default rendered format problem when calling render method without :content_type option. Closes #11393.
Merge pull request #11437 from kennyj/fix_11393

Fix #11393. Fix default rendered format when calling render method without :content_type option.
 #4566: Remove extra decrement of transaction level

`rollback_active_record_state!` tries to restore model state on `Exception`
by invoking `restore_transaction_record_state` it decrement deep level by `1`.

After restoring it ensure that states to be cleared
and level decremented by invoking `clear_transaction_record_state`,
which cause the bug: because state already reduced in `restore_transaction_record_state`.

Removed double derement of transaction level
and removed duplicated code which clear transaction state for top level.
Blacklist->whitelist for reference scans in order!

Stop special-casing Arel::Nodes as exempt from reference scanning in
order. Instead, only scan order values that are strings for a table
reference.
re-introduce `select_for_count` private method.

See https://github.com/rails/rails/commit/da9b5d4a8435b744fcf278fffd6d7f1e36d4a4f2#commitcomment-3630064 for discussion.