Bump babel-loader to fix npm warning (facebook#4776)

Author: frenzzy

package.json

@@ -27,7 +27,7 @@
     "babel-core": "7.0.0-bridge.0",
     "babel-eslint": "8.2.3",
     "babel-jest": "22.4.3",
-    "babel-loader": "8.0.0-beta.0",
+    "babel-loader": "8.0.0-beta.4",
     "babel-plugin-named-asset-import": "^0.1.0",
     "babel-preset-react-app": "^3.1.1",
     "bfj": "5.2.0",