CHANGELOG.md: add Unreleased section at the top.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

CHANGELOG.md

@@ -4,6 +4,23 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+
+### Changed
+
+### Deprecated
+
+Note: You should always set `allow-deprecated-apis=false` to test for
+changes.
+
+### Removed
+
+### Fixed
+
+### Security
+
 ## [0.6.1] - 2018-09-11: "Principled Opposition To Segwit"
 
 This release named by ZmnSCPxj.
@@ -51,9 +68,6 @@ This release named by ZmnSCPxj.
 
 ### Deprecated
 
-Note: You should always set `allow-deprecated-apis=false` to test for
-changes.
-
 ### Removed
 
 - JSON API: `listpeers` results no long have `alias` and `color` fields;