Support defined log output

Change-Id: Ibfa5b152c2b7db21c28c2dfe1c247ab5bd47d12e
diff --git a/kalamar.conf b/kalamar.conf
index 1b3e779..fe7f327 100644
--- a/kalamar.conf
+++ b/kalamar.conf
@@ -39,6 +39,9 @@
     ## Backend API version
     # api_version => '1.0',
 
+    ## Log file
+    # log_file => 'logs/kalamar.log',
+
     ## If the application is run behind a proxy, ignore the forwarded host
     # proxy_host => 0,