and fix various issue, stop pubsub blockers from halting system, improve
concurrency, add log event tags, document protobuf

Signed-off-by: Silas Davis <silas@monax.io>

implement tagging on events based on header, and add query string using
event query grammar

Signed-off-by: Silas Davis <silas@monax.io>

Signed-off-by: Silas Davis <silas@monax.io>