Added minor optimizations for syncing all entities.
zip_safe is False in setup.py so that migrations work with other apps that use django entity
Entity uses newer celery package for Django and no longer depends on djcelery
Updated versioning information for PyPI
Added EntityRelationship as an available model for the Entity API
The is_type filter returns True if there are no arguments
Renamed the cached_relationships function to cache_relationships
Updated API to change intersect_super_entities to has_super_entity_subset