Feature: added Map to CSV converter

[madisona]

This pull request adds the ability to take a [Map] and convert it to csv.

It is based on the python csv library's DictWriter: https://docs.python.org/2/library/csv.html#csv.DictWriter

[close2]

Hi, I intend to improve your PR slightly. If I don't find the time in the next few weeks, I will merge it as it is.

In any case thanks for the PR.