[WIP] Behat 3 upgrade

Upgrade to Behat 3

Changes:
- [x] Minor update on sentences
- [X] Update DemoContext to reflect changes of Behat Upgrade
- [x] Update ContentContext to reflect changes of Behat Upgrade

To do:
- [ ] make test PR (and pass on travis)
```
use EzSystems\BehatBundle\Context\Browser\Context as BrowserContext;
use EzSystems\BehatBundle\Helper\EzAssertion;
```