Overhaul how we handle notifications

- No longer orphans notifications after first event or after agent
  restarts (wtf was i doing?)
- stalker-agent now sleeps between 1-10 second on retries if initial
  notification of master fails until. Will retry notification of master
  until it succeeds
- Adds cluster wide alert flood detection and notification suppression
  (i.e. stop sending notifications if we've generated 200 alerts across
  all hosts in the last 5 minutes)
- Does away with pagerduty host based rollups
- Adds host level alert flood detection and notification suppression
  (i.e. stop sending notifications if a host has had 10 new alerts in
  the last 5 minutes)
- Adds a --state-log flag to stalker-client
- Limits state-log output web endpoint to 10 records by default
- pipeline flap counter