created custom user auth and applied it as default user
added common models app - helpers and super classes for other models
added vendors app
added products app
add products admin
initial backport of warehouse
added method and test for quickly adding products to an offer
Merge branch 'master' into app-warehousing
finished warehouse backport
added models to admin
added purchasing app
fixed warehousing models __str__ bugs
adding receiving app
stubbed sales - forgot customers need to be created first (derp brain needs coffee)
added customers app
merged in customers
finished sales app (for now)
added in model methods for weight and a4s
added shipping app