update readme links (#223)

Author: Arhell

README.md

@@ -43,14 +43,14 @@ Some of the programming design decisions reflected:
 
 PHP version 7.2 or higher is required, with the following extensions installed: 
 
-- [intl](http://php.net/manual/en/intl.requirements.php)
-- [libcurl](http://php.net/manual/en/curl.requirements.php) if you plan to use the `HTTP\CURLRequest` library
+- [intl](https://php.net/manual/en/intl.requirements.php)
+- [libcurl](https://php.net/manual/en/curl.requirements.php) if you plan to use the `HTTP\CURLRequest` library
 
 Additionally, make sure that the following extensions are enabled in your PHP:
 
 - json (enabled by default - don't turn it off)
-- [mbstring](http://php.net/manual/en/mbstring.installation.php)
-- [mysqlnd](http://php.net/manual/en/mysqlnd.install.php)
+- [mbstring](https://php.net/manual/en/mbstring.installation.php)
+- [mysqlnd](https://php.net/manual/en/mysqlnd.install.php)
 - xml (enabled by default - don't turn it off)
 
 ## Installation