is this where `contentType` should be used? or does `http.request(method, contentType)` do something else?

I wanted to check out the other custom content types that GitHub offers, e.g. the [html rendered output](http://developer.github.com/v3/media/#comment-body-properties) of markdown - but didn't know where to stick it; the `contentTypes()` method returns type `ContentType` an enum.