Add headers

I'm not a NodeJS developer so it's a bit like this:

![What](http://www.librarified.net/wp-content/uploads/2013/03/i-have-no-idea-what-im-doing-dog.jpg)

But it should be okey ^^. Ideally, we should be able to configure how much time it should be cached (I've set it to 24 hours), but I couldn't find where are the options :o.