add support Streams coding for node>=0.10

not properly tested but seems works fine:
var iconv = require('iconv-lite');
var decoder = (new iconv.StreamDecoder('koi8-r')).on('readable',function(){console.log(decoder.read())});
var buf = iconv.encode('Проверка', 'koi8-r'); // <Buffer f0 d2 cf d7 c5 d2 cb c1>
decoder.write(buf); //'Проверка'