Modified source to handle request errors, request are only processed on a status code of 200. Added interface Task, Modified GameData for multi key primary key
1. Modifed JsonRetriever to ensure that a game search request is only performed if the game has already been played. 
2. Also changed the name from JsonRetreiver to GameDataRetreiverTask.
3. Added comments to GameDataRetrieverTask
1. Modified GameDataRetrieverTask, converting json string to JSONObject, in order to retrieve the parent object's name, which is the game date and number.
1. Modified GameDataRetrieverTask, converting json string to JSONObject, in order to retrieve the parent object's name, which is the game date and number.