make use of updateItem in updates instead of put

aaaristo

We should use deepdiff to identify differences between object and _old and then create updateItem (http://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_UpdateItem.html) calls, to improve update throughput.

aaaristo

this implies making dyn.updateItem transaction-aware... so that $inc operator can be used correctly in a transaction (actually ignores the transaction).

aaaristo

fixed $inc: now is transactional

aaaristo

https://github.com/aaaristo/dyngodb/blob/master/experiments/index.updateItem.js