Fix usage of RubyRoles provisioner

I didn't initially realize that most provisioner work is actually done
on the host machine and *not* in the VM. Updated RubyRoles to instead be
given the local temp dir so it can take care of the roles there, then
those json files will be uploaded to the server and ready for chef-zero
to find them.
Ignore built gems
Update run_command to match the test-kitchen API

So #run_command is supposed to *return* the command to run on the VM, so
now concatenating the Apt command and the ChefZero command.
Update the README