readme: update with example of logging to file

examples/basic/basic.go

@@ -2,7 +2,7 @@ package main
 
 import (
 	"github.com/Sirupsen/logrus"
-	"os"
+	// "os"
 )
 
 var log = logrus.New()
@@ -10,6 +10,14 @@ var log = logrus.New()
 func init() {
 	log.Formatter = new(logrus.JSONFormatter)
 	log.Formatter = new(logrus.TextFormatter) // default
+
+	// file, err := os.OpenFile("logrus.log", os.O_CREATE|os.O_WRONLY, 0666)
+	// if err == nil {
+	// 	log.Out = file
+	// } else {
+	// 	log.Info("Failed to log to file, using default stderr")
+	// }
+
 	log.Level = logrus.DebugLevel
 }