The default stack changed from ‘cedar’ to ‘cedar-14’, so updated the
acceptance tests to reflect this.
Updating the schema makes testing easier and gives you a way to
configure the provider using env variables. It also makes the provider
more inline following the TF 0.2 approach.
cc/ @catsby if you're curious. That fixed the acceptance tests,
thought there is still one (different issue) that is still failing.
Also, it nows construct a transport instead of using the default
and setting the auth globally. TF could potentially run things
concurrently and that might go wrong.