Array类型当作泛型参数时，无法成功取值

服务端结果可能是这样的，要使用泛型支持2种结果的解析
```
{
"data": [
{"key":"value"}
],
"succeeded": true,
"message": "",
"code": 123
}
{
"data": {
"key": "value"
},
"succeeded": true,
"message": "",
"code": 123
}
```

我的代码如下
https://gist.github.com/sunbeams001/a33e0af379077b1ffd6507a1b4fd243d
```
import HandyJSON

extension Array: HandyJSON {}
extension String: HandyJSON {}
extension NSDictionary: HandyJSON {}

class ResponseData: HandyJSON {
var code: Int = 0
var data: T?
var message: String?
var succeeded: Bool = false

required init() {}

func mapping(mapper: HelpingMapper) {
mapper <<<
data <-- ("data", TransformOf(
fromJSON: { rawString in
if T.self is Array.Type && (T.self as! Array.Type).Element.self is HandyJSON.Type {
return type(of: [(T.self as! Array.Type).Element.self as! HandyJSON.Type]).deserialize(from: rawString?.toJSONString()) as? T
} else {
return T.deserialize(from: rawString?.toJSONString())
}
}, toJSON: { value in
value??.toJSONString()
}))
}
}
```

结果
ResponseData 可以成功
ResponseData<[SomeModel]> 不行，解析时 rawString 为 nil

我看issue上有些也提到这个问题，这种的有解决方案吗
#113
#342

Start with the linked gist and the ResponseData.mapping implementation, focusing on the TransformOf conversion of the data field. Reproduce the difference between ResponseData and ResponseData<[SomeModel]> using the two response shapes and the referenced issues #113 and #342. Done means both object and array generic results deserialize successfully.

Written by the indexing model from the issue text.