fix a typo
Consistent headlines & ToC

I believe the topics and their headlines should be consistent for obvious reasons. Also
Improve "request response" term typing & fix a minor typo
Explain where the acronym AJAX stands for & replace "JavaScript writer" with "JavaScript developer"
Improve grammar a bit
Improve grammar
Fix a typo
Wrap a piece of code to a code block
Fixes typo.
nodoc deprecated AR::Fixtures constant [ci skip]
fix StrongParameters example [ci skip]
update AssetTagHelper documentation [ci skip]
Fix AR::AttributeMethods#[] example [ci skip]
update AR::AttributeMethods::BeforeTypeCast docs [ci skip]
fix typo and improve example [ci skip]
fix error in AssertTagHelper documentation [ci skip]
More changes around 1.9 hash syntax

Added missing space in previous hash related commit
improve AR::AttributeMethods documentation [ci skip]
add docs to AR::AttributeMethods::BeforeTypeCast [ci skip]
read_attribute is public [ci skip]