added readme comment on /usr/local/bin/red_amber_green.rb being used to determine the traffic-light colour
added readme comment on /usr/local/bin/red_amber_green.rb being used to determine the traffic-light colour

cyber-dojo/runner_stateless,cyber-dojo/runner_stateless,cyber-dojo/runner,cyber-dojo/runner_stateless,cyber-dojo/runner,cyber-dojo/runner_stateless,cyber-dojo/runner_stateless,cyber-dojo/runner_stateless,cyber-dojo/runner_stateless