readme: add journal hook

README.md

diff --git a/README.md b/README.md
index ef6501f..e755e7c 100644
--- a/README.md
+++ b/README.md
@@ -242,6 +242,9 @@
 * [`github.com/johntdyer/slackrus`](https://github.com/johntdyer/slackrus)
   Hook for Slack chat.
 
+* [`github.com/wercker/journalhook`](https://github.com/wercker/journalhook).
+  Hook for logging to `systemd-journald`.
+
 #### Level logging
 
 Logrus has six logging levels: Debug, Info, Warning, Error, Fatal and Panic.