Cassettes

Fix broken tests.

When re-recording cassettes it has been appending new data, but not purging data that's no longer called.  I think what was happening is that the cassettes contained a mix of old urls/data and new urls/data.

You can still run into trouble if you run tests using a different version of Fog than was used to record the cassettes (and the services used have changed), but clearing out the cassettes might provide clearer error messages when that happens.