Merge pull request #260 from evandempsey/fixes

Created ProductListView to filter out inactive products.
Update documentation

How to avoid ImproperlyConfigured exceptions when extending the Product model

Signed-off-by: Martin Koistinen <mkoistinen@gmail.com>
Merge pull request #263 from mkoistinen/issue_160_documentation

Update documentation
Added structure for CheckoutSelectionViewTestCase.
Renamed CheckoutSelectionView test case to mirror view. Added extra test cases to it. Added OrderConfirmViewTestCase with test for confirm_order.