missing redis commands (e.g. streaming)

[Yannick Koechlin]

current redis.rb is missing quite a few commands that where recently added, e.g. streaming (xadd etc).

[Hendrik]

You should be able to add them here, at the end of the file: https://github.com/h2o/h2o/blob/master/lib/handler/mruby/embedded/redis.rb