CHANGELOG.md: Add unreleased changes

CHANGELOG.md

@@ -4,6 +4,11 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+### Updated
+- Update python dependencies to latest versions, including numpy 1.17.4, pandas
+0.25.3, flake8 3.7.9, pytest 5.2.2, and black 19.10b0
+
 ## [0.3.1] - 2019-10-01
 ## Changed
 - Replace non-breaking spaces (U+00A0) with space instead of removing them