Tutorial 'Data Visualization' - some improvements

[doudou]

Could you extract just the data visualization commit ?

Since it is a single commit, you can do it with

git reset --hard autobuild/master
# I got that one from the current pull request in github
git cherry-pick c294481
git push autobuild +master:data_visualization

It would allow merging it as it is pretty straightforward

[doudou]

Closing this, the relevant commit have been cherry-picked in #13