Mark Tails 2.7 as released.

debian/changelog

-tails (2.7) UNRELEASED; urgency=medium
+tails (2.7) unstable; urgency=medium
 
   * Security fixes
     - Upgrade to Linux 4.7. (Closes: #11885, #11818)
@@ -49,7 +49,7 @@ tails (2.7) UNRELEASED; urgency=medium
     - Remove DVDROM device when not used, to workaround QEMU/Libvirt
       compatibility issue. (Closes: #11874)
 
- -- Tails developers <tails@boum.org>  Mon, 03 Oct 2016 23:06:51 +0200
+ -- Tails developers <tails@boum.org>  Sun, 13 Nov 2016 14:46:04 +0100
 
 tails (2.6) unstable; urgency=medium