Update and pin yaml-js version

package.json

@@ -74,7 +74,7 @@
     "whatwg-fetch": "0.11.1",
     "worker-loader": "^0.7.1",
     "xml": "1.0.1",
-    "yaml-js": "^0.1.3"
+    "yaml-js": "0.2.0"
   },
   "devDependencies": {
     "autoprefixer": "6.6.1",