* Fix - Added missing JS method 'Composite_Availability_View::get_components_availability_string'.
* Fix - Prevent JS errors if third-party code has already started the Backbone history.
* Fix - Renamed summary element button text from 'View' to 'Edit' when the chosen product is configurable.
* Tweak - Detect scroll anchoring support and let the browser handle things when available.
* Tweak - Prevent autotransitioning if the selected product is out of stock.
* Tweak - Consider if customer is tax exempt when formatting cart item display prices.