Use strip_heredoc where possible

Following up on an observation by @rafaelfranca

https://github.com/rails/rails/pull/10170/files#r3753963

Reduce the number of gsub calls to the two cases where inputs are concatenated
from various sources and with inconsistent indentation.

Also zap extraneous spacing from the sass-rails line... presumably this is a
holdover from a previous time where this aligned the version string with an
adjacent line.
Fix StatementCache docs format [ci skip]
Fix links containing stray colons
minor edit on StatementCache documentation [ci skip]
Update to Ryan's new book per his suggestion

See https://github.com/lifo/docrails/commit/edeb98c2745cbf29725eca87332cefb4f273986a#commitcomment-2995521
Fix a typo
fix :nodoc: mark on AR::AttributeMethods::Serialization [ci skip]
hides the per thread registry instance, and caches singleton methods

Existing code was delegating to the instance with delegate
macro calls, or invoking the instance method to reach
the object and call its instance methods.

But the point is to have a clean class-level interface where
the thread local instance is hidden in the implementation.

References #11c6973.
References #10198.
update git links
Merge pull request #10204 from shmatov/update-git-links

Update github links
Corrected paramter to parameter
Add :nodoc: mark to PerThreadRegistry#method_missing [ci skip]
Merge pull request #10206 from epiclabs/nodoc_for_missing_method

Add :nodoc: mark to PerThreadRegistry#method_missing [ci skip]
use define_singleton_method instead of class_eval
Merge pull request #10207 from epiclabs/use_define_singleton_method

use define_singleton_method instead of class_eval
Merge branch 'master' of github.com:lifo/docrails
added a test suite for the postgres binary type
this shows a problem with nil values
fix for the bytea/binary nil value bug
Document collection.create! on has_many associations in ActiveRecord
Merge pull request #10212 from mariovisic/active_record_doc

Add documentation for `collection.create!` on has_many records. [ci skip]