Shifter container for Tutorials

[cedriclim1]

Problem

Currently we're relying on conda environments for HPC tutorials, see #4. It would be nice if we can set up shifter containerson HPC systems to run these things more easily: https://docs.nersc.gov/development/languages/python/python-shifter/. These containers can also be used in Jupyter notebooks which looks promising: https://docs.nersc.gov/services/jupyter/how-to-guides/#how-to-use-a-container-to-run-a-jupyter-kernel.