Use package:sky imports consistently

sky/sdk/lib/animation/animated_simulation.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 'dart:async';
 
 import 'package:newton/newton.dart';
-
-import 'timeline.dart';
+import 'package:sky/animation/timeline.dart';
 
 const double _kSecondsPerMillisecond = 1000.0;
 
 class AnimatedSimulation {
 
   AnimatedSimulation(Function onTick) : _onTick = onTick {
     _ticker = new Ticker(_tick);
   }
 
   final Function _onTick;
@@ skipping 31 matching lines @@
     _value = _simulation.x(timeInSeconds);
     final bool isLastTick = _simulation.isDone(timeInSeconds);
 
     _onTick(_value);
 
     if (isLastTick)
       stop();
   }
 
 }