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/column_link.js

@@ -0,0 +1,32 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+import { Link } from 'react-router';
+
+const ColumnLink = ({ icon, text, to, href, method, hideOnMobile }) => {
+  if (href) {
+    return (
+      <a href={href} className={`column-link ${hideOnMobile ? 'hidden-on-mobile' : ''}`} data-method={method}>
+        <i className={`fa fa-fw fa-${icon} column-link__icon`} />
+        {text}
+      </a>
+    );
+  } else {
+    return (
+      <Link to={to} className={`column-link ${hideOnMobile ? 'hidden-on-mobile' : ''}`}>
+        <i className={`fa fa-fw fa-${icon} column-link__icon`} />
+        {text}
+      </Link>
+    );
+  }
+};
+
+ColumnLink.propTypes = {
+  icon: PropTypes.string.isRequired,
+  text: PropTypes.string.isRequired,
+  to: PropTypes.string,
+  href: PropTypes.string,
+  method: PropTypes.string,
+  hideOnMobile: PropTypes.bool
+};
+
+export default ColumnLink;