add security description to systemd unit file. fixes #1011.

release/config/systemd/v2ray.service

@@ -4,6 +4,11 @@ After=network.target
 Wants=network.target
 
 [Service]
+# This service runs as root. You may consider to run it as another use for security concerns.
+# By uncommenting the following two lines, this service will run as user v2ray/v2ray.
+# More discussion at https://github.com/v2ray/v2ray-core/issues/1011
+# User=v2ray
+# Group=v2ray
 Type=simple
 PIDFile=/var/run/v2ray.pid
 ExecStart=/usr/bin/v2ray/v2ray -config /etc/v2ray/config.json