Update support

[Poshi]

Hey! Did you thought about adding support for UPDATE commands? I'm thinking on a scenario where you can start by inserting a row with the sample being processed and its status ("processing") and at the end of the workflow updating that row with the new status ("processed"). Or adding some stats based on the calculus just done.
Having support for DELETE commands would be good too, so you can have the full set of CRUD operations.