Trying to run both default and scenario tests on Travis

* Aborting rake tests if subshells fail plus attempting to make
gvm-installer less destructive for easing local verification of the
tests that run on Travis.
* Getting rubocop happy with the Rakefile, collapsing things a bit
Merge pull request #94 from meatballhat/scenario-tests-on-travis

Trying to run both default and scenario tests on Travis