Added author credit.

* `read.jsp` now displays the name of the author of that page.
* If the user is logged in when they write a page, their user ID is
linked with the page.
* All pages linked to an author ID are listed on that author’s page at
`author.jsp`.
* The three controllers (`SubmitNewStoryController`,
`SubmitNewPageController`, and `EditPageController`) all handle the
author ID when submitting new pages.