------------------
* Eliminates the limitations of supported data types.
* Change object serialization method for storing data from JSON serialization method using marshmallow (external)
library to serialization method using pickle library.
* Replace CRUD methods of redis with Hash-CRUD methods
- set(key, value) -> hset('gblackboard', key, value)
- get(key) -> hget('gblackboard', key)
- delete(key) -> hdel('gblackboard', key)
- exists(key) -> hexists('gblackboard', key)
* Remove useless setup() step and mem_ready status
* Add raise_conn_error (raise 'connection error') decorator for RedisWrapper CRUD methods
* Add save & load features