Update todo.go

have one error for line 116:

  // id := m["id"].(int)//  cannot use id (type interface {}) as type int in function argument: need type assertion
 
 id, _ := strconv.Atoi(ctx.RouteData.Params["id"])// can use this one
Update todo.go

line 62:mysql datatime format error,fixed as 2rd line
//m["post_date"] = time.Now()
m["post_date"] = time.Now().Format("2006-01-02 15:04:05")
Merge pull request #4 from dongwq/master

fixed two error when i use todo example.