Use AvailabilityChecker in InventoryOperator, add InsufficientStockException
Sorted backorders filling
Merge pull request #15 from umpirsky/inventory-availability

Use AvailabilityChecker in InventoryOperator, add InsufficientStockException
Fixed URI to documentation
Merge pull request #16 from whisller/wrong_uri_to_documentation

Fixed URI to documentation