unicorn 5.5.0.pre1

Jeremy Evans contributed the "default_middleware" configuration option:

  https://bogomips.org/unicorn-public/20180913192055.GD48926@jeremyevans.local/

Jeremy also contributed the ability to use separate groups for the process
and log files:

  https://bogomips.org/unicorn-public/20180913192449.GE48926@jeremyevans.local/

There's also a couple of uninteresting minor optimizations and
documentation additions.

Eric Wong (10):
      remove random seed reset atfork
      use IO#wait instead of kgio_wait_readable
      Merge branch '5.4-stable'
      shrink pipes under Linux
      socket_helper: add hint for FreeBSD users for accf_http(9)
      tests: ensure -N/--no-default-middleware not supported in config.ru
      doc: update more URLs to use HTTPS and avoid redirects
      deduplicate strings VM-wide in Ruby 2.5+
      doc/ISSUES: add links to git clone-able mail archives of our dependencies
      README: minor updates and additional disclaimer

Jeremy Evans (2):
      Make Worker#user support different process primary group and log file group
      Support default_middleware configuration option