[x/tour] tour: make Fibonacci solution start from 0
[x/tour] tour: make Fibonacci solution start from 0

The exercise description lists Fibonacci numbers as 0, 1, 1... but the
current solution starts printing from 1. I'm changing it so it starts
printing from 0.

Change-Id: Ib36d0f0447bd5efa110cb9302f72f575ef1bf989
Reviewed-on: https://go-review.googlesource.com/41496
Reviewed-by: Alberto Donizetti <90b16103a35511ced020676f3544f17117fb4c92@gmail.com>
X-Tour-Commit: 624453ede3b6c5a2fef96c5a2cf1d8abdad35be1

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