Adding stream support to Crystal Redis

redis_ext.cr

class Redis
  module Commands
    def xadd(stream, id, params : Hash)
      params = params.each_with_object(Array(String).new(params.size * 2)) do |(key, value), array|
        array << key << value.to_s
      end
      string_command(["XADD", stream, id] + params)
    end

    def xrange(stream, start, finish)
      string_array_command(["XRANGE", stream, start, finish])
    end
  end
end