Scifi future install commands

A great man who never existed once said, "Make it so".

After writing proclamation https://github.com/test-kitchen/test-kitchen/issues/326 I thought I'd take a stab at this.

As described in the above issue, this lets us use arbitrary install scripts which will greatly aid in adding first class puppet support.

As a bonus, this adds some specs to some things that were previously untested.