Fix message at the bottom/right of maps

It was showing a date of "12 Dec 2009" even for maps rendered today,
because I mistakenly used %m (decimal number of month) instead of %d
(decimal number of day in month).

Also improve the wording.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

ocitysmap/draw_utils.py

@@ -147,7 +147,7 @@ def add_logo(ctx, paperwidth, paperheight, logo_path,
 
     ctx.move_to(png.get_width(), png.get_height() * 0.33 + fontheight)
     today = datetime.date.today()
-    gendatetext = "This map has been rendered on %s and may not be complete or accurate." % today.strftime("%m %b %Y")
+    gendatetext = "This map has been rendered on %s and may be incomplete or inaccurate." % today.strftime("%d %b %Y")
     textwidth = max(textwidth, ctx.text_extents(gendatetext)[2])
     ctx.show_text(gendatetext)