[ja] Add 2.3, 2.4 migration guide and follow #890
Ask is defunkt
[ja] Fix grammars by review.
Merge pull request #897 from suzuki/feature/ja-add-missing-migration-guide

[ja] Add 2.3, 2.4 migration guide and follow #890
correct appendices grammar
Merge pull request #903 from okonomi/feature/ja-appendices-grammar-fix

[ja] correct grammar in appendices.rst
Merge pull request #900 from AD7six/feature/stackoverflow

Ask is defunkt
[ja] Follow #896
[ja] Fix sentence by review
Merge pull request #906 from suzuki/feature/ja-follow-896

[ja] Follow #896