Added link to Turbolinks Railscast
Using American English spellings over British style spellings
Remove duplicated accepts_nested_attributes description

there are just the same description about accepts_nested_attributes [ci skip]
fix the initializer block example and clarify

clarify that the contents of the block is expected to return a string. the previous example executed puts and the initializer got nothing.

also, made it consistent with the single-line example to be more clear as to what's going on
Fix typo
[ci skip]
Add minitest-spec-rails to guide's testing options
Fixed typo : contraints -> constraints
Changed 'args' to 'arguments' when used in places other than code with fixing few more typos
Reverted code change introduced in d45145acdc576e46a1f1719d69bec96b5bf07b0a
Reverted change in activemodel/CHANGELOG.md introduced by d45145acdc576e46a1f1719d69bec96b5bf07b0a
Typo: Migration class name would use plural
s/app\/model\//app\/models\//g
view/views, asset/assets
correct test command's typo
correct some typo in earlier commit.
fix some typos
s/Github/GitHub/
s/Textmate/TextMate/
Fix some typos
localised => localized