Add an events map
Adjust docstring for events
Add log and send-message to the events map
Make events public
Remove logging from send-message
Add a trigger-event fn
Add a :ping event
Change 'ping-pong's name to 'pong'
Check the line and trigger respective events
Don't println in the loop
Have pong use trigger-event
Correctly deref events
Remove the ping event

Pong now listens to incoming.
Pong should only trigger if line is a ping
Remove ping checking from the loop
Use when-let instead of if-let
Remove line checking from the read loop

I figure each line handler can do it's own parsing, perhaps using a
standard regex.
Bind event data into a rest arg
Add a doc string for trigger-event
Have 'register-connection use :outgoing