feat(onUpdate): accept a callback as options.onUpdate

If options.onUpdate is provided, it will be called with the stats
results of the compilation on every build.

In combination with setting options.quiet, it allows the user to
manually handle the logging of the stats.

Author: Merott

middleware.js

@@ -40,6 +40,10 @@ module.exports = function(compiler, options) {
 		process.nextTick(function() {
 			// check if still in valid state
 			if(!state) return;
+
+            // make a callback with stats
+			if(typeof options.onUpdate === 'function') options.onUpdate(stats);
+
 			// print webpack output
 			var displayStats = (!options.quiet && options.stats !== false);
 			if(displayStats &&