SCORE-162. Add single Freshener method to FreshKijiTableReader which avoids synchronous write/read

issue: https://jira.kiji.org/browse/SCORE-162
review: https://review.kiji.org/r/1683

review: https://review.kiji.org/r/1683
contributed-by: ajprax (Aaron Feldstein, afeldstein@wibidata.com)