使用苹果开源的 OrderedDictionary 替换项目中的 MMOrderedDictionary

[tisfeng]

参见 #218 (comment)

[tisfeng]

后续如果在项目中看到其他老旧的第三方库，也可以这样开个 issue 进行替换。

[Kyle-Ye]

It will be blocked by the current ObjC codebase. We may consider doing so when we finish all the usage's migration to Swift.

Most value types (struct/enum) can't be used in ObjC code.

String, Dictionary and Array is just specially ones which can be bridged to NSString, NSDictionary and NSArray.

If we replace MMOrderedDictionary with OrderedDictionary, all the ObjC code can not utilize it.

[tisfeng]

好吧，那暂时先放着，等我们 Swift 迁移完成后再来替换。