title: how to order by date django post view
body: <p>How can I order my posts from latest to oldest? I Use ordering = ['-date_posted'] for class based views. how can I do the exact thing for a function based view? 
  this is my view function:</p>
  
  <pre><code>def blog_view(request):
      posts = Post.objects.all()
      paginator = Paginator(posts, 3)
      page = request.GET.get('page')
      posts = paginator.get_page(page)
      common_tags = Post.tags.most_common()[:]
      context = {
          'posts':posts,
          'common_tags':common_tags,
      }
      return render(request, 'posts/blog.html', context)
  </code></pre>