docs: function append(key, value, req) {
    var val = this.getKey(key, req)
      , str = typeof val === 'string';
    // doesn't exist becomes the empty string
    if(val === undefined) val = new Buffer('');
    if(!(val instanceof Buffer)) val = new Buffer('' + val);
    if(!(value instanceof Buffer)) value = new Buffer('' + value);
    // coerce numbers to strings
    //val = (val + '') + value;
    //val = val.concat()
    val = Buffer.concat([val, value], val.length + value.length);
    if(str) val = val.toString();
    this.setKey(key, val, undefined, undefined, undefined, req);
    return str ? Buffer.byteLength(val) : val.length;
  }