Update adding-logic.md (add async and hook-files)

[coderofsalvation]

This will resolve:

#60
deployd/deployd#591

and new user onboarding:

5 dec 2016 @ https://gitter.im/deployd/deployd Hey folks. Sorry if this has been asked before. I need to modify some user data in onGet or onPost, but it looks like the script returns the user object before my synchronous task is completed Encryption.encrypt(this.name, function(err, result){// doing stuff that takes a long time } //user object is returned before my encryption is competed I'm a node newbie so there could be an obvious solution I'm not aware of 

[NicolasRitouet]

Great, I love documentation PRs 👍