readme error: test.py does not support --nominal flag

[luigiberducci]

Hi, thanks for your work.
I wanted to report an error in the readme, which suggest to run the nominal controller with the command

python test.py --env <env> -n <number-of-agents> --nominal --epi <number-of-episodes>

However, the --nominal flag is not argument of test.py

[syzhang092218-source]

Thanks for bringing it up! We have fixed the README.