changed the rendering function to allow rendering of some, all, or a
single post
merged restful metaphor changes into rendering code

When a post is made, the program redirects to /posts/<post-id>. This
sends a request to the rendering handler and the handler uses the
post-id in the URL to render the specified post. If no post-id is
specified (like the case of the homepage), then the first 5 posts are rendered.