chore: Upgrade Babel, Jest, Eslint (#1437)

* chore: Upgrade Prettier 1.8 -> 2.0

* chore: Upgrade Babel 6 -> 7

* chore: Upgrade eslint plugins

* chore: Add eslint import/order rules

* chore: Update flow-typed deps

webpack.config.dev.js

@@ -6,8 +6,6 @@ const developmentWebpackConfig = Object.assign(commonWebpackConfig, {
   cache: true,
   devtool: "eval-source-map",
   entry: [
-    "babel-polyfill",
-    "babel-regenerator-runtime",
     "webpack-hot-middleware/client",
     "./app/index",
   ],