* PostgreSQL hstore types are automatically deserialized from the database.
* Added `#update_columns` method which updates the attributes from the passed-in hash without calling save, hence skipping validations and callbacks. `ActiveRecordError` will be raised when called on new objects or when at least one of the attributes is marked as read only.
* Deprecated most of the 'dynamic finder' methods. All dynamic methods except for `find_by_...` and `find_by_...!` are deprecated. Here's how you can rewrite the code: