bump atom-shell version
Merge branch 'master' into art-editor
add spin.js
let's just render empty
show modal with spinner while we fetch art

Show the modal immediately, with the spinner, then do the fetch, and
once we get data, append the cards into the dom and stop the spinner.
break the cache

After updating atom-shell, it looks like the new version of chrome in
it has better caching. We need to be sure we break it.