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/components/upload_form.js

@@ -0,0 +1,46 @@
+import React from 'react';
+import ImmutablePropTypes from 'react-immutable-proptypes';
+import PropTypes from 'prop-types';
+import IconButton from '../../../components/icon_button';
+import { defineMessages, injectIntl } from 'react-intl';
+import UploadProgressContainer from '../containers/upload_progress_container';
+import { Motion, spring } from 'react-motion';
+
+const messages = defineMessages({
+  undo: { id: 'upload_form.undo', defaultMessage: 'Undo' }
+});
+
+class UploadForm extends React.PureComponent {
+
+  render () {
+    const { intl, media } = this.props;
+
+    const uploads = media.map(attachment =>
+      <div className='compose-form__upload' key={attachment.get('id')}>
+        <Motion defaultStyle={{ scale: 0.8 }} style={{ scale: spring(1, { stiffness: 180, damping: 12 }) }}>
+          {({ scale }) =>
+            <div className='compose-form__upload-thumbnail' style={{ transform: `translateZ(0) scale(${scale})`, backgroundImage: `url(${attachment.get('preview_url')})` }}>
+              <IconButton icon='times' title={intl.formatMessage(messages.undo)} size={36} onClick={this.props.onRemoveFile.bind(this, attachment.get('id'))} />
+            </div>
+          }
+        </Motion>
+      </div>
+    );
+
+    return (
+      <div className='compose-form__upload-wrapper'>
+        <UploadProgressContainer />
+        <div className='compose-form__uploads-wrapper'>{uploads}</div>
+      </div>
+    );
+  }
+
+}
+
+UploadForm.propTypes = {
+  media: ImmutablePropTypes.list.isRequired,
+  onRemoveFile: PropTypes.func.isRequired,
+  intl: PropTypes.object.isRequired
+};
+
+export default injectIntl(UploadForm);