Fixed deprecation waring by updating version check logic

[dawidurbanski]

This is a follow-up to the issue I created on wordpress.org https://wordpress.org/support/topic/deprecated-update_option-value-due-to-error-in-the-code/

And closes also the other one related: https://wordpress.org/support/topic/update_option-with-deprecated-argument/

Closes #23

[ethanosullivan]

Thanks for contributing @dawidurbanski. I'll review this and commit to prod once it checks out.