Added GetPassword function.

example/simple/main.go

@@ -8,6 +8,10 @@ func main() {
 	tui.Start()
 	defer tui.Stop()
 
+	pwd := tui.GetPassword("Password: ")
+	tui.PrintString("Got %s", pwd)
+	tui.GetString("...")
+
 	c := tui.GetMenu(
 		"Menu",
 		"Some long or short text.",

input.go

@@ -10,6 +10,12 @@ func GetString(prompt string) string {
 	return s
 }
 
+func GetPassword(prompt string) string {
+	s, err := t.ReadPassword(prompt)
+	must(err)
+	return s
+}
+
 func GetInt(prompt string) int {
 	for {
 		s := GetString(prompt)