Update CHANGES.rst

rearrange ordering of releases to match chronology

CHANGES.rst

@@ -1,10 +1,21 @@
 Changes in synapse v0.27.0-rc2 (2018-03-19)
 ===========================================
-Bugs:
+
+Pulls in v0.26.1
+
+Bug fixes:
 
 * Fix bug introduced in v0.27.0-rc1 that causes much increased memory usage in state cache (PR #3005)
+
+
+Changes in synapse v0.26.1 (2018-03-15)
+=======================================
+
+Bug fixes:
+
 * Fix bug where an invalid event caused server to stop functioning correctly,
-  due to parsing and serializing bugs in ujson library. (pulled in from 0.26.1)
+  due to parsing and serializing bugs in ujson library (PR #3008)
+
 
 Changes in synapse v0.27.0-rc1 (2018-03-14)
 ===========================================
@@ -55,16 +66,6 @@ Bug fixes:
 * Fix slow event search, switch back from GIST to GIN indexes (PR #2769, #2848)
 
 
-Changes in synapse v0.26.1 (2018-03-15)
-=======================================
-
-Bug fixes:
-
-* Fix bug where an invalid event caused server to stop functioning correctly,
-  due to parsing and serializing bugs in ujson library.
-
-
-
 Changes in synapse v0.26.0 (2018-01-05)
 =======================================