Sketch of js stopgap for external URLs, downloading files.
Merge branch 'atom-child' into atom-js-stopgap [skip ci]
disable (not error on) local sources for style up- + download
remove test for local source
Merge branch 'atom-js-stopgap' of github.com:mapbox/mapbox-studio into atom-js-stopgap [skip ci]
Merge branch 'atom-child' into atom-js-stopgap [skip ci]

Conflicts:
	index-shell.js
Nuke unused js-download class.
Too much spacing.
Nuke UI test for js-download.
Merge pull request #610 from mapbox/atom-js-stopgap

Sketch of js stopgap for external URLs, downloading files.