Minor update for the development environment

Hi all, Here's a minor merge request but (since I've not been contributing for a long time) better get your advice, I guess.

This branch:

• cleans up the .gitignore file
• updates the README to make it somehow useful
• adds Laurent, Théotime, and Marco to the contributors list (very important for the day Aevol is acquired $$$)

Sincerely.

Vincent