Work towards keeping stat-state.

  We need to keep state to record per-site stats.  THis commit
 splits the server into two parts:

   POST to /      -> Test comment.
   POST to /stats -> Get stats.

  The stats are currently zero for both spam & ham, but we can
 look them up dynamically if we need to.

  TODO: Save stats - need to work out where, probably redis.

  This updates #3.