solution for t5
solution for t6
original implementation for t7

uses a single readStream
complete callback by returning null as first arg

on success, null should be first arg since that's where
the callback is looking for an error.
solution for t8
my solution to t9
official solution to t9 using mapped operations

You can use a map to specify operations on data sets
for batch operations, the json type can be used to
specify the operation (put, get, del) and the following
fields are the actual data to manipulate.

The key can be anything and the value can apparently
be parsed from the entire json row...  I'm not sure
how it does this or why that is the functionality.