Organize sky/framework/animation

sky/framework/elements/animation/controller.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import "curves.dart";
+import "../../animation/curves.dart";
 import "timer.dart";
 
 class AnimationController extends AnimationDelegate {
   final AnimationDelegate _delegate;
   AnimationTimer _timer;
   double _begin = 0.0;
   double _end = 0.0;
   Curve _curve;
   bool _isAnimating = false;
 
@@ skipping 23 matching lines @@
     if (t == 1)
       return _end;
     double curvedTime = _curve.transform(t);
     return _begin + (_end - _begin) * curvedTime;
   }
 
   void updateAnimation(double t) {
     _delegate.updateAnimation(_positionForTime(t));
   }
 }