Adding providers to support multiple backends
a add entityfk/providers.py - Provider based abstraction to support multiple backends. Django implementation
c chg entityfk/entityfk.py - Plugging in providers into existing code
c chg entityfk/managers.py - Plugging in providers into existing code
x fix entityfk/entityfk.py - Instance ObjectDoesNotExist with provider exception, remove unreachable code, entity_ref missing a return
c chg entityfk/managers.py - adding absolute imports
c chg entityfk/providers.py - Lazy init of providers, safeguarding DjangoModelProvider, adding not-found exception
c chg entityfk/entityfk.py - Model not found exc to be similar to prev versions exc
Updating README.md
c chg entityfk/providers.py - Added support for deferred init for Django (for avoiding settings import recursion)
Merge pull request #1 from infoscout/feature/providers

Feature/providers