Mention which python packages are required

[markstock]

Hi - I'm relatively new to Python and Jupyter Notebook and didn't have many python packages installed (Fedora Linux), so I had some problems getting this tool working, especially with issues relating to which "stl" package to use: wolph/numpy-stl#47 The following line worked for me on Fedora:

pip3 install numpy laspy numpy-stl matplotlib

It would be nice to share this with folks trying this package to avoid the problems I encountered.