add test and update API call + domain structure

I just added tests and also updated the the API calls and domain data structures which are outdated.
The 429 error came up some times making the result unpredictable. I think it's related to these discussion below:
http://stackoverflow.com/questions/8963485/error-429-when-invoking-reddit-api-from-google-app-engine
https://github.com/reddit/reddit/wiki/API