Update chapter 6 exercises

[D3usXMachina]

Add colours of houses to body of zebra_owner predicate.

The puzzle can be solved without knowing the colour of the last house, but a priori we wouldn't know that.

A minimal example that yields the entire solution would be:

solvesPuzzle(Street) :- 
    Street = [_,_,_],
    member(house(green,_,_), Street),
    member(house(red,english,_), Street),
    member(house(_,spanish,jaguar), Street),
    sublist([house(_,_,snail),house(_,japanese,_)], Street),
    sublist([house(_,_,snail),house(blue,_,_)], Street),
    member(house(_,_,zebra), Street).

which yields:

Street = [house(red, english, snail), house(blue, japanese, zebra), house(green, spanish, jaguar)] .