add required min version of php to style.css
add required min version of php to style.css

per https://github.com/afragen/github-updater#wordpress-and-php-requirements
gios-asu/ASU-Web-Standards-Wordpress-Theme,gios-asu/ASU-Web-Standards-Wordpress-Theme,gios-asu/ASU-Web-Standards-Wordpress-Theme,gios-asu/ASU-Web-Standards-Wordpress-Theme