Merge pull request #7 from deshipu/master

Extra costs form
Merge pull request #8 from deshipu/master

Make DailyUseage.pricing_device optional, models tests
Merge pull request #9 from deshipu/master

A form for editing usage costs
Update setup.py

Fixed setup dependencies
Merge pull request #10 from deshipu/master

Add a plugin for synchronizing cores, fix other plugins
Merge branch 'master' of github.com:allegro/ralph_pricing

Conflicts:
	setup.py
Add some tests