Improve administration form

The current administration page can be improved by utilizing the system_settings_form()

In this way a module like Domains can create specific domain settings for Responsive Menus. In short, you can install Responsive Menu for your website, but one or more domains with a another theme can have other Responsive Menu requirements.

With the above improvement I would also recommend to remove the AJAX callback en replace this with hook_requirements() for notifying problems with libraries and form states for hide or show extra settings. Another way could be to use 'vertical tabs' for each specific Responsive Menu style.

If you have any questions about the suggested improvements, feel free to ask.