Use https for targetOutside

Tunet would redirect http://www.baidu.com to http://auth4.tsinghua.edu.cn
thus returing HTTP 200, and keepOnlineLoop would not stop,
which is not wanted when not authed.

By using https, keepOnlineLoop would break, thus causing deauth->auth->online
loop again.

README.md

@@ -27,7 +27,7 @@ USAGE:
    auth-thu [options] online [online_options]
 
 VERSION:
-   2.1.1
+   2.1.2
 
 AUTHORS:
    Yuxiang Zhang <[email protected]>

cli/main.go

@@ -235,7 +235,7 @@ func keepAliveLoop(c *cli.Context, campusOnly bool) (ret error) {
 		return
 	}
 	targetInside := "https://www.tsinghua.edu.cn/"
-	targetOutside := "http://www.baidu.com/"
+	targetOutside := "https://www.baidu.com/"
 
 	stop := make(chan int, 1)
 	defer func() { stop <- 1 }()
@@ -442,7 +442,7 @@ func main() {
 	 auth-thu [options] logout
 	 auth-thu [options] online [online_options]`,
 		Usage:    "Authenticating utility for Tsinghua",
-		Version:  "2.1.1",
+		Version:  "2.1.2",
 		HideHelp: true,
 		Flags: []cli.Flag{
 			&cli.StringFlag{Name: "username, u", Usage: "your TUNET account `name`"},