client.rb

 def command(endpoint, payload, version=@version)
      path = "/commands"

      payload = JSON.generate({'command' => command,
                               'version' => version,
                               'payload' => payload})

      debug("#{path} #{payload}")

      ret = self.class.post(
        path,
        :body => {'payload' => payload},
        :options => {
          :headers => {
            'Accept'       => 'application/json',
            'Content-Type' => 'application/x-www-form-urlencoded'
          }
        }
      )

      raise_if_error(ret)

      JSON.parse(ret.body).uuid
    end