Change top-level package name

[ambsw-technology]

A final suggestion is to change the top-level package name to something that's more meaningful (e.g. ssm_diff). A programmatic user currently imports from states which isn't necessarily obvious. The diff on a PR would be useless so don't forget to update setup.py if you go this route. Perhaps something like ssm_to_yaml could be clearer (and more Google-friendly).