Move internal record hostevent into a private hrl.
Use rd.hrl and clean up references to ss_queue (remove hard coding).

Blargh: Old (non-existent) supervisor being called for start. Fixed.
Cleanup ss_queue references (remove hard coding, include rd.hrl, pass around in state, etc...).
Handle host startup and shutdown events. There is nothing being stored in
the state{} record right now. I have to pass around something, so passing around
a blank state record makes it easier to extend in the future.
Added comment to make clear why we have a blank state record.