setuptools dependency

[zafodB]

The cloudformation-cli does not work if the setuptools package is not installed.

Attempts to issue any command, for example cfn init, fail with an ambiguous error message:

ModuleNotFoundError: No module named 'pkg_resources'

Installing setuptools fixes the issue.

It would be great if this dependency was explicitly stated in the docs, or if setuptools would get installed automatically by pip when cloudformation-cli is installed.