setHeader not chainable about exegesis

[jwalton]

This is kinda pendantic, but because setHeader() in node.js is not chainable, and I thought I'd follow suit. If node.js ever starts returning something else, it would super confusing (although that's very unlikely).

But, just like in express, the set() function is chainable and does the same thing. (Although the express one can take a hash of headers to values! We should do that, too!)

[laterne]

Thanks for the info and updating the example.