title: Putting assets and public under another folder
body: <p>I'm writing a website that assigns URLs under the root domain to various user-specified records, so I'm trying to leave as many top-level paths unused as possible. Thus, I'd like to put everything in <code>public</code>, including <code>assets</code>, under a subfolder (e.g. <code>404.html</code> would become <code>edit/404.html</code>, <code>assets/users.css</code> would become <code>edit/assets/users.css</code>, etc.). Is there a simple and sane way to do this that'll keep things like <code>image_tag</code> working?</p>