Add instructions for requirements.txt

[benjwolff]

I'm submitting a ...

• new idea

For supervised learning there exists a requirements.txt which needs to be installed beforehand via pip install --user -r requirements.txt.

There are certain ways to solve this:

• Indicate in README.md, that these packages need an install and how to install
• Add a cell to the notebooks at the very beginning, which does the install
• Creating an notebook for the purpose of installing the packages