Fix Upload/Download buttons

Brew mtime/utime

Fixes text vibrancy in popover area

Error non-intrusively if not signed into iCloud

* Fixes #9
* Fixes #23

Cake/Versionator updates

Retry for certain error types, eg. time-outs

Still not an ideal system, we shouldn’t be trying to upload if we are currently
downloading for example.

Robuster sync-model + download button works now

Support back to 10.12; Tag 1.0.2

Tag 1.0.1-2

.some