add backward compatible argument parsing

Author: wleepang

install.sh

@@ -34,7 +34,7 @@ set -x
 USAGE=$(cat <<EOF
 Install Amazon EBS Autoscale
 
-    $0 [options] [-m <mount-point>]
+    $0 [options] [[-m] <mount-point>]
 
 Options
 
@@ -110,6 +110,15 @@ done
 
 eval set -- "$PARAMS"
 
+# for backwards compatibility evaluate positional parameters like previous 2.0.x and 2.1.x releases
+# this will be removed in the future
+if [ ! -z "PARAMS" ]; then
+  MOUNTPOINT=$1
+
+  if [ ! -z "$2" ]; then
+    DEVICE=$2
+  fi
+fi
 
 # Install executables
 # make executables available on standard PATH