saglac.io v3

## The main idea of it is:
- [x] adding OpenHack
- [x] having next event for both the io and the OpenHack on the front page

## Bonus:
- [x] adding a page for workshops, we'll see if there is interest for that

## Tools:
- [x] jekyll for now, maybe we can move to something else later, if required
- [x] Zurb Foundation 5.0.3

## TODO:
- [x]  implement home page
- [x] implement "io" page
- [x] implement "openhack" page
- [x] add openhack.yml
- [x] implement "atelier" page
- [x] implement "À propos" ?
- [ ] add the OpenHack on http://openhack.github.io/
- [x] add subscribe buttons to the event pages, too
- [x] add link to Google Group
- [x] add link to Twitter
- [x] add subscribe form for mailing list
- [x] responsive