v3.1.0

Rainbows! 3.1.0 - minor updates

Small bug fixes that have been sitting around, not much but
it's already been one month since our last release.

* Unicorn dependency updated to 3.4.0, so we get IPv6 support
  and Kgio.autopush support for ":tcp_nopush => true" users.

* Optional :pool_size argument is fixed for NeverBlock and
  CoolioThreadPool users.

* Mostly minor internal code cleanups

* Sunshowers support removed, it was out-of-date and
  unmaintained.  Cramp remains supported for now.

* X-Rainbows-* response headers support removed, nobody used it.

There are severalnew features in this release not documented
here.  Consider any new features not mentioned in these release
notes to be subject to removal/renaming in future releases.