[mmell] -- Added Automation changes Create Snapshot and Delete Snapshots

@mmell 
-- Added README Snapshots
-- Added RAKE task changes
-- Added cronjob changes
@sachingade20 the comments here need clarification. I don't see how these defaults result in a 14 day retention period. It's not clear which day of the week is saved for the weekly retention. It should be Sunday or configurable. 

Maybe another way to do this is  like so

        retention: 
      daily: 14 # keep every day for <daily> days
      periodic: # every <interval> days keep one snapshot for <interval * span> days
        interval: 7 
        span: 4