Consider adding support for presence

[ianjennings]

Goal is to see connected clients on a map.

@pubnubcraig says:

It would be cool to have eon.map/char {…, presence: true, …} and have a transformPresence or just use current transform with channel param passed in. (just off the top of my head)

thing of the possibilities for join, leave/timeout and state-change events and how you would use that to customize the map or chart, like icon animation or color change, etc.

Ian says:
right now the best way is to republish presence events
a user's state parameter would supply the lat / long in the same format as eon
then from there everything would be the same, but maybe like a isPresnece parameter like you suggested in the callbacks