Release 17

This release most notably adds support for performance monitoring (via
logsearch-shipper, and identifying deployment bottlenecks) and support for
long-term, raw log archiving (via AWS S3).

 * new feature: logsearch-shipper integration, including metric collectors for
   elasticsearch/redis and a Kibana dashboard
 * new feature: enhanced event monitoring - optionally have ingestor and
   parser add timing metadata for helping to identify bottlenecks (#79)
 * new feature: archiving - optionally archive/compress all messages into AWS
   S3; includes basic scripts for restoring those archived files (#78)
 * enhancement: simplify the drain script used for blocking elasticsearch
   deploys to avoid downtime (#78)
 * change: the `host` and `sslsubject` fields in the ssl-syslog ingestor are now
   named `@ingestor.remote_host` and `@ingestor.sslsubject` (#69)
 * bug: fix logstash config issue when `logstash_parser.filters` is empty (#84)