Use AFResourceIdentifierFromReferenceObject for reference the identifier in the backing context
Use AFResourceIdentifierFromReferenceObject for reference the identifier in the backing context

Thanks @conradev for the point.
https://github.com/AFNetworking/AFIncrementalStore/pull/103#issuecomment-10517348

nataliq/AFIncrementalStore,magnetsystems/AFIncrementalStore,callzhang/AFIncrementalStore