Release new version

[glensc]

please bake new release, don't forget to update brew recipe.

I was really puzzled finding that I installed the tool using instructions from this project readme, and the installed script is totally different from what I I see in GitHub.

Appears the brew installs old version from 2017: https://github.com/moul/docker-diff/releases/tag/v1.1

➔ brew info docker-diff
moul/moul/docker-diff: stable 1.1, HEAD
Compare Docker images
https://github.com/moul/docker-diff
/usr/local/Cellar/docker-diff/1.1 (7 files, 9.2KB) *
  Built from source on 2020-04-29 at 19:41:41
From: https://github.com/moul/homebrew-moul/blob/master/docker-diff.rb
==> Options
--HEAD
	Install HEAD version
==> Caveats
Bash completion has been installed to:
  /usr/local/etc/bash_completion.d

zsh functions have been installed to:
  /usr/local/share/zsh/site-functions
➔