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/components/extended_video_player.js

@@ -0,0 +1,54 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+
+class ExtendedVideoPlayer extends React.PureComponent {
+
+  constructor (props, context) {
+    super(props, context);
+    this.handleLoadedData = this.handleLoadedData.bind(this);
+    this.setRef = this.setRef.bind(this);
+  }
+
+  handleLoadedData () {
+    if (this.props.time) {
+      this.video.currentTime = this.props.time;
+    }
+  }
+
+  componentDidMount () {
+    this.video.addEventListener('loadeddata', this.handleLoadedData);
+  }
+
+  componentWillUnmount () {
+    this.video.removeEventListener('loadeddata', this.handleLoadedData);
+  }
+
+  setRef (c) {
+    this.video = c;
+  }
+
+  render () {
+    return (
+      <div className='extended-video-player'>
+        <video
+          ref={this.setRef}
+          src={this.props.src}
+          autoPlay
+          muted={this.props.muted}
+          controls={this.props.controls}
+          loop={!this.props.controls}
+        />
+      </div>
+    );
+  }
+
+}
+
+ExtendedVideoPlayer.propTypes = {
+  src: PropTypes.string.isRequired,
+  time: PropTypes.number,
+  controls: PropTypes.bool.isRequired,
+  muted: PropTypes.bool.isRequired
+};
+
+export default ExtendedVideoPlayer;