DL2 CRL module - CITRIS tutorial notebook (phlippe#91)

* CRL tutorial

* Remove pycache files

* Store CITRIS code in a separate repository and clone it inside the notebook.

* Store datasets in a separate repository

* Improvements to Colab version

* Improvements local version

* Include cell output

Author: ddgoede

docs/index.rst

@@ -168,4 +168,5 @@ If you find the tutorials helpful and would like to cite them, you can use the f
    tutorial_notebooks/DL2/sampling/subsets.ipynb
    tutorial_notebooks/DL2/sampling/permutations.ipynb
    tutorial_notebooks/DL2/sampling/graphs.ipynb
+   tutorial_notebooks/DL2/Causality_and_CRL/citris-tutorial.ipynb