Base image on jupyter/minimal-notebook

[finalspy]

Currently the image is based on jupyter/scipy-notebook.
Despite this sounds like a great idea, we also have our own requirements and python libs versions imports which may be in conflict with the ones already installed in jupyter/scipy image (scikit lear, numpy, matplotlib ...).
Even if we could just omit those libs from Saagie's requirements this would make the jupyter image non compliant with the saagie/python ones.
As a consequence we should us build the image from jupyter/minimal one.