New ports, devel/rubygem-statsd-ruby, devel/rubygem-nsa-rails5 , and
devel/rubygem-strong_migrations: Adding these new ports, because they are
required by net-im/mastodon.

https://github.com/reinh/statsd
https://www.github.com/localshred/nsa
https://github.com/ankane/strong_migrations