NEWS: add overview section for 0.18

This mentions the things I (subjectively) thought were most likely to
either annoy people or make it worth upgrading.

diff --git a/NEWS b/NEWS
index 06876e0a7df12badf36979acb77f4553568cca71..a161514e865adadabaa81860fac1d77359ed83cd 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -1,6 +1,20 @@
 Notmuch 0.18~rc0 (2014-04-22)
 =============================
 
+Overview
+--------
+
+This new release includes some enhancements to searching for messages
+by filesystem location (`folder:` and `path:` prefixes under *General*
+below).  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. For detailed release notes, see
+below.
+
 General
 -------