Add module last_sale_price
improve module description
remove __init__.py in test
English correction typo and improvement of description
quantity instead of qty
this module is more a feature than an application
be zero division safe
extract all modules depending on sale_stock to test them separatly
Merge pull request #14 from yvaucher/port-7.0-add-last_sale_price-yvr

[ADD] last_sale_price