title: How to save the selected MKAnnotation?
body: <p>I have an app that has a mapview, and it shows 20 pins (from an Array) on the map. When the user clicks on it, it can show a bubble with a right accessory button. 
  Here come my problem: How do I know which pin was pressed?
  I heard something about the mapView:didSelectAnnotationView method, but I don't really understand how do you get the pin/callout index, so that I can get the information of the object at the same index of my Array? Thanks for any help!</p>