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/pubsub.js

@@ -0,0 +1,15 @@
+"use strict"
+
+module.exports = function() {
+	var callbacks = []
+	function unsubscribe(callback) {
+		var index = callbacks.indexOf(callback)
+		if (index > -1) callbacks.splice(index, 1)
+	}
+    function publish() {
+        for (var i = 0; i < callbacks.length; i++) {
+            callbacks[i].apply(this, arguments)
+        }
+    }
+	return {subscribe: callbacks.push.bind(callbacks), unsubscribe: unsubscribe, publish: publish}
+}