chunkHash in stats output

fixed webpack#647

Author: sokra

lib/Stats.js

@@ -195,6 +195,7 @@ Stats.prototype.toJson = function toJson(options, forToString) {
 				size: chunk.modules.reduce(function(size, module) { return size + module.size(); }, 0),
 				names: chunk.name ? [chunk.name] : [],
 				files: chunk.files.slice(),
+				hash: chunk.renderedHash,
 				parents: chunk.parents.map(function(c) {
 					return c.id;
 				})