Proper log levels.

hooks/papertrail/papertrail.go

diff --git a/hooks/papertrail/papertrail.go b/hooks/papertrail/papertrail.go
index add8dcd..71c5835 100644
--- a/hooks/papertrail/papertrail.go
+++ b/hooks/papertrail/papertrail.go
@@ -54,10 +54,11 @@
 // Levels returns the available logging levels.
 func (hook *PapertrailHook) Levels() []logrus.Level {
 	return []logrus.Level{
-		logrus.Panic,
-		logrus.Fatal,
-		logrus.Error,
-		logrus.Warn,
-		logrus.Info,
+		logrus.PanicLevel,
+		logrus.FatalLevel,
+		logrus.ErrorLevel,
+		logrus.WarnLevel,
+		logrus.InfoLevel,
+		logrus.DebugLevel,
 	}
 }