Update CHANGES.md

CHANGES.md

 # Changelog
 
-## 1.18 (unreleased)
--   Return coinc FAR as well as uploading to GraceDb.
+## 1.18 (2020-03-02)
+-   Return coinc FAR as well when uploading to GraceDb.
+
+-   Calculate joint FAR for low significance GRBs in order to run RAVEN on
+    events in the joint LVK-Fermi and LVK-Swift targeted searches.
+
+-   In query, add filter for searches. This is so that can run separates
+    searches/search windows for GRB vs SubGRB events.
 
 
 ## 1.17 (2019-09-08)