Lock down version of webpack 2 to pre schema validation

- let the dust settle on validation changes webpack/webpack#2974

package.json

@@ -24,7 +24,7 @@
     "lab": "^8.0.2"
   },
   "dependencies": {
-    "webpack": "https://github.com/webpack/webpack",
+    "webpack": "2.1.0-beta.22",
     "webpack-dev-middleware": "^1.4.0"
   }
 }