Custom Events should be synchronous by default

Most custom events should be synchronous.  This allows handlers for
onBeforeBoomerangBeacon to fire before the beacon is sent so they
have the ability to modify the beacon.

The only event that should be asynchronous is the onBoomerangLoaded
event since that needs to fire after all plugins have loaded.

boomerang.js

@@ -154,20 +154,35 @@ if (!BOOMR.plugins) { BOOMR.plugins = {}; }
 	}
 }());
 
-dispatchEvent = function(e_name, e_data) {
+/**
+ dispatch a custom event to the browser
+ @param e_name	The custom event name that consumers can subscribe to
+ @param e_data	Any data passed to subscribers of the custom event via the `event.detail` property
+ @param async	By default, custom events are dispatched immediately.
+		Set to true if the event should be dispatched once the browser has finished its current
+		JavaScript execution.
+ */
+dispatchEvent = function(e_name, e_data, async) {
 	var ev = createCustomEvent(e_name, {"detail": e_data});
 	if (!ev) {
 		return;
 	}
 
-	BOOMR.setImmediate(function() {
+	function dispatch() {
 		if(d.dispatchEvent) {
 			d.dispatchEvent(ev);
 		}
 		else if(d.fireEvent) {
 			d.fireEvent("onpropertychange", ev);
 		}
-	});
+	}
+
+	if(async) {
+		BOOMR.setImmediate(dispatch);
+	}
+	else {
+		dispatch();
+	}
 };
 
 // visibilitychange is useful to detect if the page loaded through prerender
@@ -1126,7 +1141,7 @@ if (!BOOMR.xhr_excludes) {
 
 }());
 
-dispatchEvent("onBoomerangLoaded", { "BOOMR": BOOMR } );
+dispatchEvent("onBoomerangLoaded", { "BOOMR": BOOMR }, true );
 
 }(window));