Stubbing not working as desired when returning an error

[notABluesSinger]

Stubbing out the provider to return a 404 if the iin is '111111' doesn't work as expected, as the functional code moves onto the next provider, which is not stubbed out and performs a genuine http request (you can tell as mocha prints out the request time)

[jamescogley]

Provider tests should all be mocked using nock now including the invalid iin requests in #33