Good idea. It would be useful to integrate it with the routing definitions of popular frameworks. Example: generate the definition file from Rails' routes.rb
Why the example in README uses sudo by default? It seems more suitable to install APIs into local user directory by default and don't force the users to run your command as root.
You need to install it globally and it needs to be able to copy files into /usr. I reckoned this is how its down with global npm installations. Do you have any other solution?
It can take collections from Postman and run them. Commandcar seems to be more driven towards interactivity though, which is kinda cool.
Disclaimer: I work on Newman as a part of my day job.