reference-trie 0.21.0

Simple reference trie format
Documentation
# Changelog

The format is based on [Keep a Changelog].

[Keep a Changelog]: http://keepachangelog.com/en/1.0.0/

## [Unreleased]

## [0.20.0] - 2020-02-07
- Update trie-root to v0.16.0 and memory-db to v0.19.0 [#78]https://github.com/paritytech/trie/pull/78