Add systemd unit files

Signed-off-by: Jonathan McCrohan <jmccrohan@gmail.com>

README.md

@@ -28,8 +28,8 @@ To use the telnet server, you need to add a configuration that runs:
 
     nyancat -t
 
-We recommend `openbsd-inetd`, but `xinetd` will work as well, and you should be
+We recommend `openbsd-inetd`, but both `xinetd` and `systemd` work as well. You
-able to use any other compatible `inetd` flavor.
+should be able to use any other compatible `inetd` flavor too.
 
 ## Distribution Specific Information
 

systemd/nyancat.socket

@@ -0,0 +1,9 @@
+[Unit]
+Description=nyancat socket
+
+[Socket]
+ListenStream=23
+Accept=true
+
+[Install]
+WantedBy=sockets.target

systemd/nyancat@.service

@@ -0,0 +1,12 @@
+[Unit]
+Description=nyancat
+Documentation=man:nyancat(1)
+
+[Service]
+User=nobody
+ExecStart=-/usr/bin/nyancat -t
+StandardInput=socket
+StandardOutput=socket
+
+[Install]
+WantedBy=multi-user.target