Use 'responses' library to mock the requests for testing.

This will allow us to test creates and destroys as well
as the readonly actions.

See: http://cramer.io/2014/05/20/mocking-requests-with-responses/
https://github.com/dropbox/responses
Don't use assertItemsEqual as it is not available in Python3
Mock test_auth_fail as well
Merge pull request #70 from andrewsomething/test-improvements

Use 'responses' library to mock the requests for testing.