Fix for bug #546, added docs for event listeners on the host element.

added section on imperatively declared event listeners
mem
Language lawyer sidebar: Steve's going to laugh at me, but to avoid Arv et al becoming sad, we (me included) have to get out of the habit of calling `publish`, e.g., a `block`. `blocks` are code statements between curly-braces. Name/value pairs between curly-braces are are `objects` or `object literals`