Remove XMLHttpRequest dependency injection in the API - always use the global; tweak the jasmine mock for xhr; hits "Not Implemented" error.
Start updating Client.get to match test spec; problem: I do not have net access and cannot lookup XMLHttpRequest API.
Update to a "bare-bones complete implementation" based on reading XHR docs.
Update the test expectation to fully specify XHR usage and callback semantics of the Client.get API.
Update implementation to match spec.