Return errors when the resource URL does not have an ID or the object...

... isn't available.

Closes #21 
super minor but I think there is `success?`  method available on the response object. http://rubydoc.info/gems/faraday/0.5.3/Faraday/Response

This feels a little wonky but I don't have a better suggestion. Feel free to tell me to :shipit: