fix to be able to compile on Windows

[stunndard]

By default, code like this won't compile on Windows because of some missing definitions in Windows:

// daemonizing
    if config.Cfg.IsDaemon && runtime.GOOS == "linux" {
        logger.Log("Daemon mode, detaching from terminal...", logger.LOG_INFO)

        cntxt := &daemon.Context{
            PidFileName: config.Cfg.PidFile,
            PidFilePerm: 0644,
            //LogFileName: "log",
            //LogFilePerm: 0640,
            WorkDir: "./",
            Umask:   027,
            //Args:        []string{"[goicy sample]"},
        }

        d, err := cntxt.Reborn()
        if err != nil {
            logger.File(err.Error(), logger.LOG_ERROR)
            return
        }
        if d != nil {
            logger.File("Parent process died", logger.LOG_INFO)
            return
        }
        defer cntxt.Release()
        logger.Log("Daemonized successfully", logger.LOG_INFO)
    }

This change will use empty functions for Windows and will allow it to compile on Windows when creating cross-platform apps that use go-daemon on Linux, and don't use it for Windows. This change won't affect compilation on Linux in any way. I think go-daemon should follow the standard Golang naming convention which is used by Google:

For example:
your_package_linux.go
your_package_darwin.go
your_package_windows.go

You could see how it is implemented in standard os/signal package for example: https://github.com/golang/go/tree/master/src/os/signal

your_package_posix.go is not following this convention and gets picked up and compiled on Windows, which is wrong.

[sevlyar]

You are right. I forgot about +build directive. Thank you for contributing!