set version to 2.0.0-beta2

update Changes to 2.0.0-beta1

update Changes for 1.7.1

releng for 1.7.0

Merge pull request h2o#738 from h2o/kazuho/libressl-2.2.6

update to libressl 2.2.6

releng for 1.6.3

releng for 1.7.0-beta4

releng for 1.7.0-beta3

releng for 1.6.2

Merge branch 'kazuho/mruby-update-to-725b3ca'