Fix tax calculator with non-VAT taxes.

This is an issue with Spree line items and tax rate calulators.

The method used to subtract tax from a VAT did not play nicely
with non value added taxes.

Fixes #2870
Bump to selenium-webdriver 2.32.0

Conflicts:
	common_spree_dependencies.rb
Recalculate product count_on_hand when ANY of its variants are saved

Fixes #2799

Conflicts:
	core/app/models/spree/variant.rb