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
- [x] Streams
- [x] Validation
- [x] Validation using joi object
- [x] Uploads
- [x] Cookies

I'll finish the others tomorrow or this weekend.
Fixes #100