Simplify Travis config and fix ChefDK 2.0 failures
Simplify Travis config and fix ChefDK 2.0 failures

mawatech/postfix,mawatech/postfix,chef-cookbooks/postfix,opscode-cookbooks/postfix,opscode-cookbooks/postfix,gnowxilef/cookbook-postfix,chef-cookbooks/postfix,gnowxilef/cookbook-postfix