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

app/javascript/mastodon/features/ui/containers/modal_container.js

@@ -0,0 +1,16 @@
+import { connect } from 'react-redux';
+import { closeModal } from '../../../actions/modal';
+import ModalRoot from '../components/modal_root';
+
+const mapStateToProps = state => ({
+  type: state.get('modal').modalType,
+  props: state.get('modal').modalProps
+});
+
+const mapDispatchToProps = dispatch => ({
+  onClose () {
+    dispatch(closeModal());
+  },
+});
+
+export default connect(mapStateToProps, mapDispatchToProps)(ModalRoot);