move HelloWorld to be a peer of SampleApp

example/mac/HelloWorldNSView.mm

-//
-//  SkExampleNSView.m
-//  SkiaExamples
-//
-//  Created by Sergio González on 6/11/13.
-//
-//
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
 
-#import "SkExampleNSView.h"
+#import "HelloWorldNSView.h"
 
 #include "SkApplication.h"
 #include <crt_externs.h>  
 
-@implementation SkExampleNSView
+@implementation HelloWorldNSView
 
 - (id)initWithDefaults {
     if ((self = [super initWithDefaults])) {
         fWind = create_sk_window(self, *_NSGetArgc(), *_NSGetArgv());
     }
     return self;
 }
 
 - (void)dealloc {
     delete fWind;
     [super dealloc];
 }
 
 @end