Added a poem for the #+BEGIN_VERSE example.

This used to be Einstein's quote, but this is already in use for
demonstrating #+BEGIN_QUOTE.  I've picked up AlexSchroeder's Haiku
as found here:  http://www.emacswiki.org/cgi-bin/wiki/EmacsHaiku

doc/org.texi

@@ -6859,8 +6859,11 @@ can use this construct, which can also be used to format poetry.
 
 @example
 #+BEGIN_VERSE
-Everything should be made as simple as possible,
+ Great clouds overhead
-but not any simpler -- Albert Einstein
+ Tiny black birds rise and fall
+ Snow covers Emacs
+ 
+     -- AlexSchroeder
 #+END_VERSE
 @end example