Updating client dependencies. Switching to yarn. (#6433)

* Updating client dependancies. Switching to using yarn.

* Updating React

* Moving pure components to using function syntax (performance gains with newer react version)

* Updating client dependancies.

* Ignore .yarninstall

* Enabling pre-lockfile because it's the entire point of using yarn.

* Removing old webpack config

* Moving to new prop-types

* Fixing ESLint Errors

* Updating jest snapshots.

* Cleaning up package.json

webapp/components/sidebar_right_menu.jsx

@@ -28,6 +28,8 @@ import {FormattedMessage} from 'react-intl';
 import {Link} from 'react-router/es6';
 import {createMenuTip} from 'components/tutorial/tutorial_tip.jsx';
 
+import PropTypes from 'prop-types';
+
 import React from 'react';
 
 export default class SidebarRightMenu extends React.Component {
@@ -527,6 +529,6 @@ export default class SidebarRightMenu extends React.Component {
 }
 
 SidebarRightMenu.propTypes = {
-    teamType: React.PropTypes.string,
-    teamDisplayName: React.PropTypes.string
+    teamType: PropTypes.string,
+    teamDisplayName: PropTypes.string
 };