fix #821 : converted the getting_started.rst file as a Jupyter notebook

Author: alixdamman

doc/source/tutorial.rst

@@ -12,7 +12,7 @@ It is mainly dedicated to help new users to familiarize with it and others to re
 .. toctree::
    :maxdepth: 2
 
-   ./tutorial/getting_started.rst
+   ./tutorial/getting_started.ipynb
    ./tutorial/tutorial_presenting_larray_objects.ipynb
    ./tutorial/tutorial_IO.ipynb
    ./tutorial/tutorial_transforming.ipynb