remove call to travis_run_flake8 from .travis.yml
fix mutable object as method arg default value

use states=None in sale_order.action_invoice_create() which is interpreted in
the parent class implementation as meaning ['confirmed', 'done', 'exception']
Merge pull request #45 from gurneyalex/7.0-fix-pylint

fix mutable object as method arg default value
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