Adding Support for Custom JSONSubscriptType - #376

enum J : String {
    case Id = "id"
    case ChannelId = "channel_id"
    case ChannelTitle = "channel_title"
    case Title = "title"
    case Template = "template"
    case Articles = "articles"
}

extensions J : JSONSubscriptType {
    var jsonKey:JSONSubscriptKey {
        return JSONSubscriptKey.Key(self.rawValue)
    }
}

let idNumber = j[J.ChannelId].number ?? j[J.Id].number ?? NSNumber(int: 0)