Cannot load Atomic-Chrome extension in Chrome in developer mode

Current behaviour:
When trying to load the atomic-chrome extension manually from a git repo, it doesn't work.

I get an error message saying the following:

Error Loading Extension
Failed to load extension from: ~/git/atomic-chrome/app
Could not load background script 'scripts/background.js'.

Expected behaviour:
Should be possible to load extension from a copy of the source, or there should be instructions explaning how to make it work.

Versions:
Linux: Debian 4.9.51-1
Chrome: Version 63.0.3239.84 (Official Build) (64-bit)

Steps to reproduce:
1. Clone repo to ~/git
git clone https://github.com/tuvistavie/atomic-chrome.git
2. Open chrome://extensions in Chrome
3. Tick "Developer Mode"
4. Click "Load unpacked Extension" and navigate to git repo on local storage

I tried both the top level directory and the app directory for this.