Make travis validate json
Created by: kBite
As I broke
vagrant.json (#21) and fixed it (#22) I want to prevent this.
At https://travis-ci.org/kBite/arch-boxes/builds/266753922 you find
.travis.yml output building my branch which is based on master and fails as expected.
packer version is currently hardcoded, because there is no 'latest' (see hashicorp/packer/issues/5265).