Rename rendering/render_*.dart to rendering/*.dart

sky/examples/raw/ink_well.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:sky' as sky;
 import 'package:sky/framework/app.dart';
-import 'package:sky/framework/rendering/render_box.dart';
-import 'package:sky/framework/rendering/render_node.dart';
+import 'package:sky/framework/rendering/box.dart';
+import 'package:sky/framework/rendering/node.dart';
 import 'package:sky/framework/animation/animated_value.dart';
 import 'package:sky/framework/animation/curves.dart';
 
 const double _kInitialSize = 0.0;
 const double _kTargetSize = 100.0;
 const double _kSplashDuration = 500.0;
 const int _kInitialOpacity = 0x80;
 
 class InkSplash {
   final InkWell inkWell;
@@ skipping 42 matching lines @@
     for (InkSplash splash in _splashes)
       splash.paint(canvas);
   }
 }
 
 AppView app;
 
 void main() {
   app = new AppView(new InkWell());
 }