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/member_list_team/member_list_team.jsx

@@ -13,6 +13,8 @@ import Constants from 'utils/constants.jsx';
 
 import * as UserAgent from 'utils/user_agent.jsx';
 
+import PropTypes from 'prop-types';
+
 import React from 'react';
 
 import store from 'stores/redux_store.jsx';
@@ -22,9 +24,9 @@ const USERS_PER_PAGE = 50;
 
 export default class MemberListTeam extends React.Component {
     static propTypes = {
-        isAdmin: React.PropTypes.bool,
-        actions: React.PropTypes.shape({
-            getTeamStats: React.PropTypes.func.isRequired
+        isAdmin: PropTypes.bool,
+        actions: PropTypes.shape({
+            getTeamStats: PropTypes.func.isRequired
         }).isRequired
     }