Add backends as explicit package
Include backends as explicit package

Thought this would be included by default!

gh-37
Add leftover modules to package list

Closes gh-38
Fixes issue validating org ownership

The `save` method on `OrganizationOwner` validates that the linked
`OrganizationUser` actually belongs to the right organization instance,
but in comparing against a model inhereting directly from the
`Organziation` class it compares the intended `CustomModel` instance to
the underying `Organization` instance, and it fails.

Closes gh-39
Version bump
Updates changelog
Merge branch 'master' into dev

Conflicts:
	setup.py