request-headers

Requests the headers of a URL and then aborts the request.

``
requestHeaders('https://foaas.herokuapp.com/you/finn/finn', function(err, statusCode, headers) {
console.log('Content type: ' + headers['content-type']);
});
`
It is similar to the npm module curli, but curli` uses the HEAD command,
which might be a better idea. However am not sure how well implemented HEAD
is across the web therefore I rather abort a GET.