Add readme and improve start script

README.md

+- GitHub: https://github.com/Yelp/elastalert
+- ReadTheDocs: https://elastalert.readthedocs.io/en/latest/

tasks/main.yml

-# ElastAlert
-# https://github.com/Yelp/elastalert
-
 ---
 # file: roles/elastalert/tasks/main.yml
 

templates/etc_init_d_elastalert

@@ -18,12 +18,10 @@ case "$1" in
         echo "Starting ElastAlert ..."
         cd /opt/elastalert
         /usr/local/bin/elastalert &
-        exit 0
         ;;
     stop)
         echo "Stoping ElastAlert ..."
         kill `pidof /usr/bin/python /usr/local/bin/elastalert` && echo "ElastAlert stopped"
-        exit 0
         ;;
     restart)
         $0 stop
@@ -35,4 +33,4 @@ case "$1" in
         ;;
 esac
 
-exit $?
+exit 0