__iter__ should always return iterator object instance
__iter__ should always return iterator object instance

python expects that __iter__ returns only iterator instances, so we must ensure this always happen, not sure if there are any cases where get_value() itself might return iterator object, but I doubt it since it's used to get the value from the cache and we can't store object instances there, only values
fixes #3
iurisilvio/Flask-SQLAlchemy-Cache