refactor redraw into pubsub and autoredraw

- pubsub is a basic pubsub impl
- autoredraw is glue code to register callback to pubsub and onevent

moved e.redraw to autoredraw

api/autoredraw.js

@@ -0,0 +1,17 @@
+"use strict"
+
+var throttle = require("../api/throttle")
+
+module.exports = function(root, renderer, pubsub, callback) {
+	var run = throttle(callback)
+	renderer.setEventCallback(function(e) {
+		if (e.redraw !== false) run()
+	})
+	
+	if (pubsub != null) {
+		if (root.redraw) pubsub.unsubscribe(root.redraw)
+		pubsub.subscribe(run)
+	}
+	
+	return root.redraw = run
+}