* Set up ahoy gem, add ahoy-js
* Import ahoy.js into base.js.erb
* Add trackNotification function to notifications/index.html.erb
* Add sanitized_broadcast_id helper
* Use sanitized_broadcast_id in broadcast partial
* Add specs around tracking welcome notifications
* Remove optional fields from Ahoy::Visit migration + table
* Fiddle with trait to see if it helps with CI failures
* Disable geocode tracking in ahoy
* Stub out SiteConfig in notifications page spec
