Encoding the page response in 'binary' so consumer could decode in non-nodejs charsets

In order to support non-nodejs charset like 'GBK' we need to encode the page response in 'binary' so consumer could decode the strings correctly. An example as in routers-news:

var title = iconv.decode(element.text(), 'gb2312');
Merge pull request #3 from yonggao/patch-1

Encoding the page response in 'binary' so consumer could decode in non-nodejs charsets