Merge branch '8.x-1.x' into unit-tests

.circleci/build.sh

.circleci/config.yml

.circleci/deploy.sh

.circleci/lint.sh

.circleci/process-artifacts.sh

.circleci/test.sh

.travis.yml

README.md

composer.json

modules/recurring_events_registration/README.md

...stall/recurring_events_registration.registrant.config.yml

...on/config/schema/recurring_events_registration.schema.yml

...events_registration/recurring_events_registration.install

..._events_registration/recurring_events_registration.module

...egistration/recurring_events_registration.post_update.php

...s_registration/recurring_events_registration.services.yml

...ents_registration/recurring_events_registration.views.inc

...s/recurring_events_registration/src/Entity/Registrant.php

...ing_events_registration/src/Form/RegistrantDeleteForm.php

...recurring_events_registration/src/Form/RegistrantForm.php