[WIP] Behat upgrade

Upgrade to Behat 3

Biggest changes:
- [x] subcontexts to traits (need to change inheritances and interface implementations)
- [x] RegEx to Turnip (horray!)
- [x] Update the feature sentences to refelct better the actual actions
- [x] Refactor REST drivers
- [x] chained steps were dropped (workaround needed)

To do:
- [ ] make test PR (and pass on travis)