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/components/confirmation_modal.js

@@ -0,0 +1,51 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+import { defineMessages, injectIntl, FormattedMessage } from 'react-intl';
+import Button from '../../../components/button';
+
+class ConfirmationModal extends React.PureComponent {
+
+  constructor (props, context) {
+    super(props, context);
+    this.handleClick = this.handleClick.bind(this);
+    this.handleCancel = this.handleCancel.bind(this);
+  }
+
+  handleClick () {
+    this.props.onClose();
+    this.props.onConfirm();
+  }
+
+  handleCancel (e) {
+    e.preventDefault();
+    this.props.onClose();
+  }
+
+  render () {
+    const { intl, message, confirm, onConfirm, onClose } = this.props;
+
+    return (
+      <div className='modal-root__modal confirmation-modal'>
+        <div className='confirmation-modal__container'>
+          {message}
+        </div>
+
+        <div className='confirmation-modal__action-bar'>
+          <div><a href='#' onClick={this.handleCancel}><FormattedMessage id='confirmation_modal.cancel' defaultMessage='Cancel' /></a></div>
+          <Button text={confirm} onClick={this.handleClick} />
+        </div>
+      </div>
+    );
+  }
+
+}
+
+ConfirmationModal.propTypes = {
+  message: PropTypes.node.isRequired,
+  confirm: PropTypes.string.isRequired,
+  onClose: PropTypes.func.isRequired,
+  onConfirm: PropTypes.func.isRequired,
+  intl: PropTypes.object.isRequired
+};
+
+export default injectIntl(ConfirmationModal);