Added environment variable PM2_GRACEFUL_LISTEN_TIMEOUT to define how much time pm2 will wait for the child process to send a listening event in cluster mode before sending the shutdown message to the old process
Merge branch 'master' of https://github.com/adrianocola/PM2 into adrianocola-master
Merge branch 'adrianocola-master' into development
add GRACEFUL_LISTEN_TIMEOUT variable to conf file