Merge pull request #2 from AsymmetricVentures/backend-removal

Backend removal
Update documentation

Custom backend not needed anymore
Revert "Temporary bugfix."

This reverts commit a20e43e13e8d9a8a38d2eda131df009ca297aaee.
Test DictionaryField is pickable
Fix AttributeError

If self.connection is missing, an AttributeError is raised.
Got this error while using rest_framework, but still not found how
HStoreDict is missing of 'connection' attribute
Fix: wrong implementation of __getstate__ protocol
Merge https://github.com/AsymmetricVentures/django-hstore
Merge branch 'backend-removal'