Django-grainy

Added
- Permissions.instances(): add `explicit` keyword argument
- Permissions.instances(): add `ignore_grant_all` keyword argument
- Permissions.check(): add `ignore_grant_all` keyword argument

Added
- Passing a `tuple` or `list` to `helpers.namespace` will now return a joint namespace of all contained elements
- Implemented `util.Permissions.instances` method to retrieve all instances of a model according to permissions
- `decorators.grainy_view` decorator can now use url parameters to format it s namespace

Added
- grainy authentication backend
- django admin integration
- str_flags function
- PermissioManager.add_permission
- Default permissions for AnonymousUser
- decorators.grainy_view
- decorators.grainy_rest_viewset
- helpers.dict_get_namespace
- helpers.request_method_to_flag
- helpers.request_to_flag
- util.Permissions.grant_all property
- conf.REQUEST_METHOD_TO_FLAG
Fixed
- util.Permissions now accepts AnonynmousUser as object
Changed
- renamed `convert_flags` to `int_flags`
- moved `str_flags` and `int_flags` functions from util.py to helpers.py
- moved `namespace` function from util.py to models.py
- removed `clear` argument from `PermissionManager.add_permission_set`