Make list informative, stop arg panics

For list command, precede the output with the name of the node.

For run, eval, test commands, stop panic when no params and give
informative error.
I was wrong about the string method, I forgot that we were defining that node within the config struct, so what i suggested wasn't workable.
as a work around, I just made the change here more readable
please see: https://github.com/compose/transporter/pull/10/files