correct the release date

ba790a06 · Anton Akhmerov · Christoph Groth · 2f52e84a · ba790a06
Commit ba790a06 authored Sep 09, 2013 by Anton Akhmerov Committed by Christoph Groth Sep 09, 2013
--- a/doc/source/pre/whatsnew/1.0.rst
+++ b/doc/source/pre/whatsnew/1.0.rst
 What's new in Kwant 1.0
 =======================

-This article explains the user-visible changes in Kwant 1.0, released on 8
+This article explains the user-visible changes in Kwant 1.0, released on 9
 September 2013.