Bug! Should've ignored format string in logs

Minimal case,

```
func main () {
    log.Println ("Hello There! %Y %s", "123")
}
```

And you will see this in fresh,

```
15:24:52 app         | 2016/05/16 15:24:52 Hello There! %!Y(MISSING) %!s(MISSING) 123
```
