Add changelog for v0.25.1

Author: ashleyvega

CHANGELOG.md

@@ -1,5 +1,15 @@
 # Changelog
 
+## 0.25.1
+
+*2020-10-14*
+
+This release backports two fixes from the forthcoming 0.26.0 release.
+
+### Improvements
+- [#2354](https://github.com/vegaprotocol/vega/pull/2354) Update `OrderEvent` to copy by value
+- [#2379](https://github.com/vegaprotocol/vega/pull/2379) Add missing `/governance/prepare/vote` REST endpoint
+
 ## 0.25.0
 
 *2020-09-24*

README.md

@@ -1,6 +1,6 @@
 # Vega
 
-Version 0.25.0.
+Version 0.25.1.
 
 A decentralised trading platform that allows pseudo-anonymous trading of derivatives on a blockchain.