Specs: rename sky:core to dart:sky

sky/specs/gestures.md

 Gestures
 ========
 
 ```dart
 SKY MODULE
-<!-- part of sky:core -->
+<!-- part of dart:sky -->
 
 <script>
 abstract class GestureEvent extends Event {
   Gesture _gesture;
   Gesture get gesture => _gesture;
 }
 
 class GestureState {
   @nonnull bool cancel = true; // if true, then cancel the gesture at this point
   @nonnull bool capture = false; // (for PointerDownEvent) if true, then this pointer is relevant
@@ skipping 237 matching lines @@
 
 }
 </script>
 ```
 
 Gestures defined in the framework
 ---------------------------------
 
 ```dart
 SKY MODULE
-<!-- not in sky:core -->
+<!-- not in dart:sky -->
 <!-- note: this hasn't been dartified yet -->
 
 <script>
 class TapGesture extends Gesture {
 
   // internal state:
   //   Integer numButtons = 0;
   //   Boolean primaryDown = false;
 
   virtual GestureState processEvent(Event event);
@@ skipping 146 matching lines @@
   // fling-end: cancel(), or after fling or fling-cancel (prechoose)
 }
 
 class FlingLeftGesture : FlingGesture { }
 class FlingRightGesture : FlingGesture { }
 class FlingUpGesture : FlingGesture { }
 class FlingDownGesture : FlingGesture { }
 
 </script>
 ```