The repo contains *.bak files

A few *.bak files exist in the repo that should be removed.

```
$ find . -name "*.bak" -delete -print
./hyperstack/api_client.py.bak
./hyperstack/exceptions.py.bak
./hyperstack/rest.py.bak
./hyperstack/api_response.py.bak
./hyperstack/__init__.py.bak
```
