Store end user facing flatfiles in Google Cloud Storage buckets

[jrlegrand]

Problem Statement

We currently export mart flatfiles to AWS s3 buckets thanks to the diligent work of our interns Miles and Komal.

With the move to BigQuery, it makes more sense to store these in GCS buckets.

This is not a huge priority, but will be nice to be all under one roof.

Criteria for Success

Mart flatfiles exported to GCS buckets.

Additional Information

Goal is to coalesce around a single ecosystem (Google).

[jrlegrand]

I would consider this resolved by PR #299 - obviously some additional fine-tuning of access and things like that will be needed, but the basic functionality is there.