add answers to exercise 1-6 chapter 8

[ryblovAV]

Hi, @axel22
Pls see my changes

[axel22]

I'm surprised that this shows that travis.yml is added, when it is already in the repository.

[axel22]

Nice!
Please address my comments, and I will merge this in.

[ryblovAV]

Thanks for the reply, I'll try to fix

[ryblovAV]

@axel22,
pls see my changes

[axel22]

You should never receive an error from an actor to whom you sent PlusMoney, no?

[axel22]

Thanks! I left a couple of minor comments.

[ryblovAV]

Hi, @axel22
Thanks for you recommendation,
Maybe I should use the Akka persistence (http://doc.akka.io/docs/akka/current/scala/persistence.html) in exercise 2 ?

[axel22]

No, if actors can arbitrarily fail, the only thing you can do is to implement a consensus algorithm and replicate the state of all the bank accounts across multiple actors.

That exercise is meant as a thought experiment to convince yourself of how hard this problem actually is.

[axel22]

LGTM! Thanks a lot!

[ryblovAV]

Thanks !!!