Installation description issues

[vitknobloch]

When installing I faced a couple issues with versions and missing dependencies, but it's a quick fix:

• gitman must be installed with pip. pip install gitman
• scikit-learn is missing from dependencies for map.py script, but is required. pip install scikit-learn
• setuptools version < 58.0.0 is needed for demjson to install (one of the subdependencies of map.py script). pip install setuptools~=57.5.0

[novosma]

Thank you a lot for this! Added to the README!