German translation added
Added Ulrich Wagner to AUTHORS
Merge.
added recalculate_billship_tax util to update billship_handler and tax_handler when cart is modified after first step
removed extra spaces
Merge.
Added Justin McKeon to AUTHORS.
Combine recalculate_discount and recalculate_billship_tax into a single function recalculate_cart.
Update travis config.
Bump minimum Mezzanine version to 1.4.15
Version bump to 0.8.4
Added tag 0.8.4 for changeset 5be0adbb4b3b
Update auto-generated changelog, requirements.
Merge branch 'master' of github.com:stephenmcd/cartridge into rebase-upstream

Conflicts:
	cartridge/shop/views.py