fix specs to test writing hashes with symbol keys
dump Oj with strings as keys, raise error if trying to load a dumped document that doesn't have a _type
add comment
refactor load_scraped_object method
resolve foreign keys on foreign objects
update comments
transform model schema to hash
fix resolution of foreign keys in foreign objects, if objects already persisted
move transformation of hash keys into a module
fix bug in case the partial resolution of an object changes some properties