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/team_settings.jsx

@@ -6,6 +6,8 @@ import ImportTab from './team_import_tab.jsx';
 import GeneralTab from './team_general_tab.jsx';
 import * as Utils from 'utils/utils.jsx';
 
+import PropTypes from 'prop-types';
+
 import React from 'react';
 
 export default class TeamSettings extends React.Component {
@@ -73,7 +75,7 @@ TeamSettings.defaultProps = {
 };
 
 TeamSettings.propTypes = {
-    activeTab: React.PropTypes.string.isRequired,
-    activeSection: React.PropTypes.string.isRequired,
-    updateSection: React.PropTypes.func.isRequired
+    activeTab: PropTypes.string.isRequired,
+    activeSection: PropTypes.string.isRequired,
+    updateSection: PropTypes.func.isRequired
 };