Use type information to infer object type

[mjallday]

Currently the python client uses meta classes and URLs to specify the type of object.

The API now returns type information (see _type param below) on all resources when they are returned. Using this instead allows us to break away from inspecting the URL to see the type of object that something is and gives us more flexibility in naming conventions.

$ curl https://api.balancedpayments.com/v1/api_keys -X POST
{
  "_type": "api_key", 
  "created_at": "2013-05-06T21:37:38.888923Z", 
  "uri": "/v1/api_keys/AK1m8dgKozaJwrv1BaYBesYn", 
  "_uris": {}, 
  "meta": {}, 
  "id": "AK1m8dgKozaJwrv1BaYBesYn"
}