Add feature to skip `pip install`

Details in the README and `start-storm.sh` script

Signed-off-by: Pang Yan Han <yanhan@viki.com>
start-storm.sh - require single arg `all` for starting everything

And change the behavior of running the script without any arguments to
show the help.

Signed-off-by: Pang Yan Han <yanhan@viki.com>