Log Message:
Update ruby-kgio to 2.8.0.

=== kgio 2.8.0 - TCP Fast Open, writev/trywritev / 2013-01-18 10:52 UTC

  TCP Fast Open in Linux 3.7 and later is now supported
  in the client via Kgio::Socket#kgio_fastopen.

  This release also adds the kgio_writev and
  kgio_trywritev methods, thanks to funny-falcon