debian: changelog stanza for 0.18

plagiariaze my own summary from upstream NEWS

debian/changelog

@@ -1,3 +1,21 @@
+notmuch (0.18-1) unstable; urgency=medium
+
+  * New upstream release. For detailed release notes see
+    see /usr/share/doc/notmuch/NEWS.gz. Some highlights:
+    - Changes/enhancements to searching for messages by filesystem
+      location ('folder:' and 'path:' prefixes).
+    - Saved searches in Emacs have also been enhanced to allow
+      distinct search orders for each one.
+    - Another enhancement to the Emacs interface is that replies to
+      encrypted messages are now encrypted, reducing the risk of
+      unintentional information disclosure.
+    - The default dump output format has changed to the more robust
+      'batch-tag' format.
+    - The previously deprecated parsing of single message mboxes has
+      been removed.
+
+ -- David Bremner <bremner@debian.org>  Tue, 06 May 2014 16:20:39 +0900
+
 notmuch (0.18~rc1-1) experimental; urgency=low
 
   * Upstream release candidate