update tutorial function with more appropiate one from Eric Smith

Doc/tutorial/controlflow.rst

@@ -445,8 +445,8 @@ called with an arbitrary number of arguments.  These arguments will be wrapped
 up in a tuple.  Before the variable number of arguments, zero or more normal
 arguments may occur. ::
 
-   def fprintf(file, template, *args):
-       file.write(template.format(args))
+   def write_multiple_items(file, seperator, *args):
+       file.write(seperator.join(args))
 
 
 .. _tut-unpacking-arguments: