Private Site Plugin

<?php
/*
Plugin Name: Private Site
Description: Site is only viewable by logged in users.
Author: c.bavota
Version: 1.0.0
Author URI: http://www.bavotasan.com/
*/
class Bavotasan_Private {
    public function __construct() {
        add_action( 'init', array( $this, 'init' ) );
    }

    public function init() {
        if ( ! is_user_logged_in() && ! $this->is_login() ) {
            wp_redirect( wp_login_url() );
            exit;
        }
    }

    public function is_login() {
        return in_array( $GLOBALS['pagenow'], array( 'wp-login.php', 'wp-register.php' ) );
    }
}
$bavotasan_private = new Bavotasan_Private;