IB version churn
added Sparkle support for auto-updates

- it only gets included for `dist` builds with setup.py (so local `app`
builds can be modified without being immediately ‘upgraded’)
- menu item only appears if the framework is present
- prefs window still needs to be wired-up to SUUpdater
- xml feed still needs to be posted (and url added to info.plist)
no longer including the full offline docs

(since they basically triple the app’s size)
pointer to the web docs

- and presumably there’ll be a link on the site to download an offline
copy
store the sparkle sources somewhere sensible