Unable to delete command which name contains '/'

I was experimenting with commands which were prefixes of eachother...
```bash
$ cat some.cmd | ssh alpha.cmd.io :create u/a/b/c
Command u/a/b/c already exists
$ ssh alpha.cmd.io :delete u/a/b/c
Command not found: u/a/b/c
```
altough these can be created...they are not callable currently.
It would be either good to:

* prevent the creation of command which contains '/'
* or support them...

I think it would be practical to not support commands which contains '/' in their name.