[WIP] Feature/git helpers

Feature branch for:
- Git helpers
- "Gulp" deploy command (deploy CSS/JS files, which are compiled locally, to the target server)

More infos:
https://divio-ch.atlassian.net/browse/TECH-1
'manage.py collectstatic' gathers quite a few files so I didn't want to go into that. `./static/css/` and `./static/js/` are the folders managed by front-end, but we should confirm with @FinalAngel