Honor flattened attribute in model for rest-json
Fix test to not depend on inner xml order
Use a patched os.environ in tests

Don't use global state (os.environ) as this messes with tests.
Instead use the BaseEnvVar class that patches out os.environ for you.
This was causing a test fail because a test was depending on os.environ
being patched to have the access/secret key env vars available.
Merge branch 's3-flattened-fix' into develop

Closes #67

* s3-flattened-fix:
  Use a patched os.environ in tests
  Fix test to not depend on inner xml order
  Honor flattened attribute in model for rest-json