Switch examples to Babel 7, Jest 23, and Webpack 4 (reduxjs#3155)

* Update async example

* Update counter example

* Update real-world example

* Update shopping-cart example

* Update todomvc example

* Update todos example

* Update todos-flow example

* Update todos-with-undo example

* Update tree-view example

* Fix warnings

* Switch test environments to node

* Ignore empty tests

* Update snapshots

Author: Timer

examples/async/package-lock.json

@@ -3,7 +3,7 @@
   "version": "0.0.1",
   "private": true,
   "devDependencies": {
-    "react-scripts": "^1.1.4"
+    "react-scripts": "^2.0.2"
   },
   "dependencies": {
     "prop-types": "^15.6.1",
@@ -18,6 +18,12 @@
     "start": "react-scripts start",
     "build": "react-scripts build",
     "eject": "react-scripts eject",
-    "test": "react-scripts test"
-  }
+    "test": "react-scripts test --env=node --passWithNoTests"
+  },
+  "browserslist": [
+    ">0.2%",
+    "not dead",
+    "not ie <= 11",
+    "not op_mini all"
+  ]
 }