Updates for compatibility with Hapi 8.0 (WIP)

Exercises updated:
- [x] Hello_hapi
- [x] Routes
- [x] Handling
- [x] Directories
- [x] Views
- [x] Proxies
- [x] Helping
- [ ] Streams
- [ ] Validation
- [ ] Validation using joi object
- [ ] Uploads
- [ ] Cookies

I'll finish the others tomorrow or this weekend.