Add search-help to the book page.

templates/book/books.html.ep

@@ -2,6 +2,10 @@
 % title 'Books';
 <h1><%= title %></h1>
 
+Some books have no associated author. To search for these, use
+author like '[no author]'.
+
+<p/>
 <%# On a new search, reset the page number to 1. %>
 %= form_for books => { page_number => 1 } => begin
 %= label_for title_like => 'Title like'