Move last-updated-at to Preface chapter

byte_of_python.asciidoc

@@ -17,9 +17,6 @@
 or guide to the Python language for a beginner audience. If all you know about computers is how to
 save text files, then this is the book for you.
 
-The book was last updated at {docdatetime} and generated using
-http://www.asciidoctor.org[AsciiDoctor] {asciidoctor-version}.
-
 include::frontpage.asciidoc[]
 
 include::dedication.asciidoc[]

preface.asciidoc

@@ -52,7 +52,9 @@ In the true spirit of open source, I have received lots of constructive suggesti
 
 === Status Of The Book
 
-- Latest update of this book was in Mar-Apr 2014, converted to
+- The book was last updated on {docdate} and generated using
+  http://www.asciidoctor.org[AsciiDoctor] {asciidoctor-version}.
+- Last major update of this book was in Mar-Apr 2014, converted to
   http://asciidoctor.org/docs/what-is-asciidoc/[Asciidoc] using
   http://swaroopch.com/2013/10/17/emacs-configuration-tutorial/[Emacs 24] and
   https://github.com/sensorflo/adoc-mode/wiki[adoc-mode].