Update tutorial to hapi v17 about learn-hapi

[nelsonic]

@iteles I've had this open in my browser for the past couple of weeks:

• 17.0.0 Release Notes: hapijs/hapi#3658
• Review the new v17: hapijs/hapi#3623
• https://medium.com/netscape/async-iterators-these-promises-are-killing-my-performance-4767df03d85b
• https://medium.com/@bluepnume/learn-about-promises-before-you-start-using-async-await-eb148164a9c8

I haven't been able to find a performance comparison between Hapi v16 vs. Hapi v17 ... 🔍
As far as I can tell it's a stylistic update that forces the entire community to re-write their apps. 💄
Hence low on list of "priorities" (compared to other client work...) ⬇️

[iteles]

@Danwhy, yes, that would be excellent.
An overview of the key differences would also be useful at this early transition stage.

[sledorze]

@nelsonic I think the content of this issue is highly relevant and shades some lights on the behaviour of a better execution model.
funfix/funfix#37

[Danwhy]

Should we leave a small section of the tutorial around v16?
Maybe just a link to the current state of this repo (https://github.com/dwyl/learn-hapi/tree/b58495ea002a9f3f8af8d183f6004d2b483f4591) would be enough?

[nelsonic]

A few dependencies out-of-date: https://david-dm.org/dwyl/learn-hapi

Going to update them now.

[nelsonic]

devDependencies are up-to-date: https://david-dm.org/dwyl/learn-hapi?type=dev