Modernize followercounthistory insight

Modified CountHistoryDAO::getHistory to take a parameter to specify data-points needed
  to calculate a trend.
Added insight tests
Modified the follower count insight to be generated with at least 5 data-points
Added example docs to CountHistory::getHistory and added debug output to tests
Spiced up the copy
Modified CountHistoryDAO::getHistory to stop filling in missing data
Added tests for CountHistoryMySQLDAO and insights to handle missing vis_datapoints.