title: how to display a countdown timer
body: <p>I can't figure out how to do this.
  I have a button and once it's tapped I want to start a process in five seconds and while the user is waiting i want to show the count down - 5, 4, 3, 2, 1</p>
  
  <p>I can't get this to work i've tried using nstimer but that doesn't work.
  Any suggestions?
  Thankds</p>