adds an event buffer to hold events from raft changes.
update events to use event buffer
fix append call
provide way to prune buffer items after TTL
event publisher tests
basic publish test
wire up max item ttl
rename package to stream, cleanup exploratory work
subscription filtering
subscription plumbing
allow subscribers to consume events, handle closing subscriptions
back out old exploratory ctx work
fix lint
remove unused ctx bits
add a few comments
fix test
stop publisher on abandon
