new port: www/rubygem-unicorn-worker-killer

Kill unicorn workers by memory and request counts

WWW: https://rubygems.org/gems/unicorn-worker-killer

PR: 199927
Differential Revision: https://reviews.freebsd.org/D2496
Submitted by: Michael Fausten <ports@michael-fausten.de>
Approved by: mat (mentor)