Added webpack.ProvidePlugin for most used imports

Removed imports of React, connect, PropTypes throughout
Removed the "React" in React.Component/PureComponent

app/javascript/gabsocial/features/groups/timeline/containers/header_container.js

@@ -1,4 +1,3 @@
-import { connect } from 'react-redux';
 import Header from '../components/header';
 import { joinGroup, leaveGroup } from '../../../../actions/groups';