Login and register view cleanup/style fixes.

I can't help but shake the feeling that the logic in these two views is similar
enough to be in its own view helper. Even still, I'm reluctant to essentially
recreate Zend\Form\View\Helper\Form because that's what it would probably look like.

I welcome feedback as to what should be done here. (It's not a pressing matter.)
Set HttpOnly flag for session cookies.

Closes #87.

Setting the HttpOnly flag for session cookies (and just cookies in general) helps mitigate
the risk of a client-side script accessing the cookie [1]. An HttpOnly session cookie will
be used only when responding to HTTP requests.

[1]: https://en.wikipedia.org/wiki/HTTP_cookie#HttpOnly_cookie