Replace sprockets/browserify with Webpack (#2617)

* Replace browserify with webpack

* Add react-intl-translations-manager

* Do not minify in development, add offline-plugin for ServiceWorker background cache updates

* Adjust tests and dependencies

* Fix production deployments

* Fix tests

* More optimizations

* Improve travis cache for npm stuff

* Re-run travis

* Add back support for custom.scss as before

* Remove offline-plugin and babili

* Fix issue with Immutable.List().unshift(...values) not working as expected

* Make travis load schema instead of running all migrations in sequence

* Fix missing React import in WarningContainer. Optimize rendering performance by using ImmutablePureComponent instead of
React.PureComponent. ImmutablePureComponent uses Immutable.is() to compare props. Replace dynamic callback bindings in
<UI />

* Add react definitions to places that use JSX

* Add Procfile.dev for running rails, webpack and streaming API at the same time

config/webpack/production.js

@@ -0,0 +1,44 @@
+// Note: You must restart bin/webpack-dev-server for changes to take effect
+
+/* eslint global-require: 0 */
+
+const webpack = require('webpack')
+const merge = require('webpack-merge')
+const CompressionPlugin = require('compression-webpack-plugin')
+const sharedConfig = require('./shared.js')
+
+module.exports = merge(sharedConfig, {
+  output: { filename: '[name]-[chunkhash].js' },
+
+  plugins: [
+    new webpack.optimize.UglifyJsPlugin({
+      compress: {
+        unused: true,
+        evaluate: true,
+        booleans: true,
+        drop_debugger: true,
+        dead_code: true,
+        pure_getters: true,
+        negate_iife: true,
+        conditionals: true,
+        loops: true,
+        cascade: true,
+        keep_fargs: false,
+        warnings: true
+      },
+
+      mangle: false,
+
+      output: {
+        comments: false
+      },
+
+      sourceMap: false
+    }),
+    new CompressionPlugin({
+      asset: '[path].gz[query]',
+      algorithm: 'gzip',
+      test: /\.(js|css|svg|eot|ttf|woff|woff2)$/
+    })
+  ]
+})