2013-12-17 - Jonathan Morgan - added ability to just update data rows for active sub-reddits, not deal with inactive sub-reddits in a given time period.  Also added variance to count statistics, and added count of unique authors within time period.
2013-12-17 - Jonathan Morgan - added ability to just update active rows to example file, and added a detailed note explaining when you'd want to only update time-series rows where there was activity.