Upgrade to CircleCI 2 - Githubissues

CircleCI 1 will stop working on August 31st 2018.

[x] Write a .circleci/config.yml in Formation--Modele (in a branch)
[x] Remove circle.yml from Formation--Modele (in the same branch)
[x] Open a PR, make me a reviewer, squash the PR after green light
[x] Notify training maintainers that they need to patch their training repos before 2018-08-31 by cherry-picking the commit resulting from the PR

Zenika-Training / zenika-formation-framework