panic on missing cmd

[ChrisPenner]

Currently rargs completely panics if you pass it a program it can't exec; I'd expected it to fail of course, but maybe with a slightly better message 😄

$ cat myfile.txt | rargs something
thread '<unnamed>' panicked at 'command failed to start: Os { code: 2, kind: NotFound, message: "No such file or directory" }', src/libcore/result.rs:1165:5
...

It prints the panic for each line of the input file.

Thanks for the tool! I've been looking for something handy like this 👍