added: grape-entity gem
added: entities folder for custom serialization using grape-entity
added: Applicants endpoint now uses grape-entity
fixed: specs don't use entities
improved: specs
refactor
added: shared specs for all actions
refactor
refactor
added: accepted column to applicants table
added: :accepted to applicants serializer
added: accept action to the applicants endpoint with specs
added: more specs for the accept action
refactor