Plugin Remediation

[nicholasio]

Hi, we at 10up are migrating a client to our enviroment and as part of that we have audit some of the plugin used by the client. We found some small issues with your plugin and this Pull Request addresses them.

It basically fixes the following:

• Plugin options were deleted on plugin deactivation, this should be done when uninstalling the plugin.
• Several variables were missing escaping (Late Escaping)
• I also fixed some PHPCS issues regarding the code style.
• Usually it is not a good idea to use the php closing tag (?>) on php only files as it can cause the "Headers already sent" issue.

Let me know if you have any question!

Thanks for the plugin.