WordPress: Customize URL for default registration on wp-login page.

custom-wp-login-register-url.php

<?php

/**
 * Customize URL for default registration on wp-login page.
 * Add to functions.php
**/
function wp_kompanee_register_url($link){
    //Change wp-login registration url
    return str_replace(site_url('wp-login.php?action=register', 'login'),site_url('register', 'login'),$link);
}
add_filter('register', 'wp_kompanee_register_url');

function wp_kompanee_fix_register_urls($url, $path, $orig_scheme){
//Override other default registration links
//http://en.bainternet.info/2012/wordpress-easy-login-url-with-no-htaccess
    if ($orig_scheme !== 'login')
        return $url;

    if ($path == 'wp-login.php?action=register')
        return site_url('register', 'login');

    return $url;
}
add_filter('site_url', 'wp_kompanee_fix_register_urls', 10, 3);