Add support for batch deletes

[JoshZA]

This would be super handy

http://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_BatchWriteItem.html

[Incubatio]

Here is a part of the code I use for BatchWrite PutRequest using vogel Model and its validation: https://gist.github.com/Incubatio/7c56d90897fff9ff0eb4

Just replace PutRequest by DeleteRequest and you have your batch delete.

Note that batchWrite support only 25 item at a time, so you might want to create chunk (with _.chunk for instance) Another note, when you have huge amount of data, you might want to use waterfall or series to avoid too many concurrent threads.