Update README.md

README.md

@@ -50,7 +50,7 @@ import "github.com/prologic/bitcask"
 func main() {
     db, _ := bitcask.Open("/tmp/db")
     defer db.Close()
-    db.Put("Hello", []byte("World"))
+    db.Put([]byte("Hello"), []byte("World"))
     val, _ := db.Get("Hello")
 }
 ```