0.003   2018-03-15 (PERLANCAR)

	- [opt] Merge purchases with same price to the last inventory
	  record.


0.002   2018-03-15 (PERLANCAR)

	- [Incompatible change] Remove summary() and replace it with units() and
          average_purchase_price().

        - Add argument: allow_negative_inventory.

        - sell() now returns realized profits.


0.001   2018-03-09 (PERLANCAR)

        - First release.