WIP on OrderableListMixin
Add basic ordering to OrderableListMixin
Refactor test class name
Test if only allowed columns can be used for ordering
Test default ordering column
Test if raises ImproperlyConfigured when no Orderable.default
Add docs for OrderableListMixin
Improve style: qs -> queryset
Improve style: use double quoutes
Improve style: dont break lines with \
Improve style: dont fetch GET params twice
Improve style: OrderableListMixin.get_queryset as two steps
Improve style: ctx -> context
Remove model.Orderable in favor of view vars
Merge remote-tracking branch 'upstream/master' into orderable-list-mixin
Add OrderableListMixin.get_orderable_columns() method
Raise ImproperlyConfigured if OrderableListMixin.orderable_columns is None
Add OrderableListMixin.get_orderable_columns_default() + tests
Refactor tests
Improve the readme to reflect changes in #45