Well, that was quicker than I expected.
- Manual journal create/update/view (can only create draft invoices for now)
- Inventory items create/update/view
- Invoice line items can now be specified with the item_code which uses defaults for the item from Xero
- PDF versions of invoices and credit notes can be retrieved with the Invoice#pdf([filename]) method
- Payments can now have a reference specified on creation.
As always, remember this library is still only alpha-quality, so please make sure to test, test, test.