Get a zset buffer.
function zset(obj, vonly) {
  var vtype = this.type(3)
    , key = !vonly ? this.getStringBuffer(obj.key) : new Buffer(0)
    , length = obj.length !== undefined
        ? obj.length : Object.keys(obj.value).length
    , len = this.getLengthEncoding(length, false)
    , value = this.object(obj.value);
  return Buffer.concat(
    [
      vtype,
      key,
      len,
      value
    ],
    vtype.length + key.length + len.length + value.length
  )
}