键值数据存储
基于文件的键值数据存储，支持基本CRD（创建，读取和删除）操作。
用法
import KVDS
# Initializing the class with filename and filepath,
# if filepath is not specified the json file will save
# into current working directory
kvds = KVDS(filename=FILE_NAME, filepath=FILE_PATH)
#T
