Add DELETE permission to the eventlog table.

Without this, an application user who is not owner of the database/table
(or superuser) can't delete events after sending them out.

Fixes #101.

nakadi-producer-spring-boot-starter/src/main/resources/db_nakadiproducer/migrations/V2/V2133546886.1.2__grant_delete_permissions.sql

@@ -0,0 +1 @@
+GRANT DELETE ON nakadi_events.event_log TO PUBLIC;