wrong status code of middleware

the example of gin should be:

``` go
// StatMiddleware response time, status code count, etc.
func StatMiddleware() gin.HandlerFunc {
    return func(c *gin.Context) {
        beginning, _ := Stats.Begin(c.Writer)
        c.Next()
        Stats.EndWithStatus(beginning, c.Writer.Status())
    }
}
```

the example of  martini has same issue
