* The live api is now split into two methods. One that fetches the data
and deserializes the json the second that creates the model instances.
These two methods are wrapped by the live method. The split is useful
when working with multiple threads. One worker thread that fetches
the data and the main thread that creates the instances.
* added LiveTopic model since the topic data in the live api doesn't
contain all the data that a Topic contains.
* makes sure that the _synced attribute is set when calling sync directly.
groups now know their topics and topics know their messages.
the relevant convore apis are:
- /groups/:group_id/topics.json
- /topics/:topic_id/messages.json