CE/map_follow_behavior

created custom "follow me" behavior to keep user centered on the map after pressing the "follow me" button.  if the user pans or zooms the map while in following mode following is cancelled.  
Much like what you saw with the formatted classes, this could be made a designated initializer so the behavior always has a map. Then you could also make the `mapView` property read only. 

Not necessary, but could be something to think about.