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/compose/containers/upload_progress_container.js

@@ -0,0 +1,9 @@
+import { connect } from 'react-redux';
+import UploadProgress from '../components/upload_progress';
+
+const mapStateToProps = (state, props) => ({
+  active: state.getIn(['compose', 'is_uploading']),
+  progress: state.getIn(['compose', 'progress'])
+});
+
+export default connect(mapStateToProps)(UploadProgress);