Update default minitest-chef-handler Gem version

minitest-chef-handler stopped working due to a dependency issue
that has been fixed in 1.0.3 (see
https://github.com/calavera/minitest-chef-handler/pull/82).  So
we want to default to the fixed version.
Merge pull request #64 from mfischer-zd/master

Update default minitest-chef-handler Gem version