drop doc#book endpoint

This is from an old mock-up of the book code. It doesn't
actually work (it returns a 500 probably because the
database schema has changed). The real endpoint is "/books",
so let's redirect there.

app/views/doc/book.html.erb

@@ -1,35 +0,0 @@
-<%- @section    = 'documentation' %>
-<%- @subsection = 'book' %>
-<%- @page_title = "Git - Book" %>
-
-<% content_for :sidebar do %>
-  <%= render 'translations' %>
-<% end %>
-
-<div id='main'>
-  <h1>Book</h1>
-  <img style="float:right;margin: -20px 40px 0 40px;" src="/images/books/pro-git@2x.jpg" width="118" height="157" />
-  <p>
-  The entire Pro Git book, written by Scott Chacon and Ben Straub and published by Apress, is available here. All content is licensed under the <a href="https://creativecommons.org/licenses/by-nc-sa/3.0/">Creative Commons Attribution Non Commercial Share Alike 3.0 license</a>.  Print versions of the book are available on <a href="http://www.amazon.com/gp/product/1430218339?ie=UTF8&camp=1789&creative=9325&creativeASIN=1430218339&linkCode=as2&tag=git-sfconservancy-20">Amazon.com</a>.</>
-  </p>
-  <ol class='book-toc'>
-    <% @book.chapters.each do |chapter| %>
-    <li class='chapter'>
-    <h2><%= chapter.number %>. <a href="/book/<%= @book.code %>/<%=u chapter.sections.first.slug %>"><%=raw chapter.title %></a></h2>
-      <ol>
-        <% chapter.sections.each do |section| %>
-          <% if !section.title.empty? %>
-            <li>
-              <%= chapter.number %>.<%= section.number %>
-              <a href="/book/<%= @book.code %>/<%= u(section.slug) %>"><%=raw section.title %></a>
-            </li>
-          <% end %>
-        <% end %>
-      </ol>
-    </li>
-    <% end %>
-    <li class='chapter'>
-      <h2><a href="/book/commands">Index of Commands</a></h2>
-    </li>
-  </ol>
-</div>

app/views/doc/book_section.html.erb

@@ -1,14 +0,0 @@
-<% @section    = 'documentation' %>
-<% @subsection = 'book' %>
-
-<% content_for :sidebar do %>
-  <%= render 'translations' %>
-  <%= render 'shared/related' %>
-<% end %>
-
-<div id='main' class="book">
-  <% if !@content.title.empty? %>
-    <h1><%= @content.cs_number %> <%=raw @content.chapter.title %> - <%=raw @content.title %></h1>
-  <% end %>
-  <div><%=raw linkify(@content.html, @content) %></div>
-</div>

config/routes.rb

@@ -86,7 +86,7 @@ Gitscm::Application.routes.draw do
   get "/documentation" => "doc#index"
   get "/documentation/reference" => "doc#ref"
   get "/documentation/reference/:file.html" => "doc#man"
-  get "/documentation/book" => "doc#book"
+  get "/documentation/book" => redirect("/book")
   get "/documentation/videos" => "doc#videos"
   get "/documentation/external-links" => "doc#ext"