Derived from https://github.com/tinifni/gntp-notify
Weechat must be built with the ruby option enabled. If using homebrew
$ brew install weechat --with-ruby
Then, make sure to use system ruby
# using *system ruby*
$ sudo gem install weechat terminal-notifier
$ curl https://raw.github.com/wallace/weechat-notification-center-rb/master/notification_center.rb > ~/.weechat/ruby/autoload/notification_center.rb
$ sudo weechat # for Yosemite