Updated the serializer/* articles to Symfony 4#8687

Merged

weaverryan merged 3 commits intosymfony:masterfrom

javiereguiluz:update_serializer

Nov 21, 2017

Commits on Nov 16, 2017

Updated the serializer/* articles to Symfony 4
javiereguiluz
committed

Commits on Nov 17, 2017

Fixed a reference
javiereguiluz
committed

Commits on Nov 19, 2017

Fixed a RST reference
javiereguiluz
committed