Test on Chef 13 / 14. Chef 12 is EOL
Test on Chef 13 / 14. Chef 12 is EOL

Signed-off-by: Tim Smith <764ef62106582a09ed09dfa0b6bff7c05fd7d1e4@chef.io>

chef-cookbooks/squid,opscode-cookbooks/squid,opscode-cookbooks/squid,chef-cookbooks/squid