Pin package versions

Author: Timer

packages/react-scripts/package.json

@@ -49,12 +49,12 @@
     "graphql-tag": "2.9.2",
     "html-webpack-plugin": "3.2.0",
     "identity-obj-proxy": "3.0.0",
-    "loader-utils": "^1.1.0",
     "jest": "23.5.0",
-    "mini-css-extract-plugin": "^0.4.0",
+    "loader-utils": "1.1.0",
+    "mini-css-extract-plugin": "0.4.0",
     "object-assign": "4.1.1",
+    "optimize-css-assets-webpack-plugin": "4.0.1",
     "postcss-flexbugs-fixes": "3.3.1",
-    "optimize-css-assets-webpack-plugin": "^4.0.1",
     "postcss-loader": "2.1.5",
     "promise": "8.0.1",
     "raf": "3.4.0",