batcave: renew proxy letsencrypt certs weekly
    
    We occasionally run into problems with certs that aren't renewed in time
    or are close to expiring. Just running the proxies playbook will renew
    them, but in freezes or the like sometimes there's a long time period
    where we don't run that playbook.
    
    So, lets just run weekly with the right tag. This should renew any cert
    thats close to expiring.
    
    The job shouldn't normally output anything, but if there's errors it
    will email them to admin@
    
    Signed-off-by: Kevin Fenzi <kevin@scrye.com>