v0.5.0

• Add support for using Celery as the background worker
• Allow persisting and management of child entities via the Aggregate object
• Add support for Dict serialization
• Store Reference and Value Object fields in Entity.meta_ for later use
• Allow Subscribers and Handlers to hook into multiple Domain Events
• Raise InvalidDataError on invalid attributes to Commands
• Treat meta attributes like auto_fields and mandatory_fields as dictionaries instead of tuples
• Add support for nested serializers/schemas with Marshmallow
• Bugfix #304 - Remove shadow object linkages with aggregates
• Bugfix to not link shadow fields with Aggregate/Entity classes directly
• Bugfix to set initialize Shadow (Reference) and Value Object attributes correctly
• Bugfix to avoid fetching child records without foreign key linkages