Update 'Content-Length' value for fix characters missing

[EthianWong]

In other languages (Chinese , Japanese .... ) One word maybe use two or three bytes ...

var a = "我爱你";
console.log(a.length); //3
console.log(new Buffer(a).length); //9

So you should use new Buffer for set "Content-Length" and this problem will be resolve

[CLAassistant]

All committers have signed the CLA.

[niemyjski]

Thanks a ton, I'll review these changes tomorrow!

[niemyjski]

This is a duplicate of #65