新增会员 统计
按年查询 2018
预期响应：
"num": 3, "time": "03", "lastnum": 0, "growth": 0 "num": 2, "time": "04", "lastnum": 0, "growth": 0
按年查询 2017
预期响应
null
按月查询 2018-04
预期响应
"num": 1, "time": "12", "lastnum": 0, "growth": 0 "num": 1, "time": "22", "lastnum": 2, "growth": "-50%"
按月查询 2018-05
预期响应
null