title: try, try! & try? what’s the difference, and when to use each?
body: <p>In <a href="http://ahmedabdurrahman.com/2015/08/22/swift-2-0/">Swift 2.0</a>, Apple introduced a new way to handle errors (do-try-catch).
  And few days ago in Beta 6 an even newer keyword was introduced (<code>try?</code>).
  Also, knew that I can use <code>try!</code>.
  What's the difference between the 3 keywords, and when to use each?</p>