feat: added parsed headers to response object

[adampash]

I don't know if this is something you're interested in adding, but I needed the response headers in the response, and this PR adds them. It also adds another dependency, which you might not want.

Anyway, I am using browser-request for a node/web project, and it's been great! I just needed this one adjustment to make it compatible with the response object from node request.

Thanks!

(Oh also, apologies for the semi-colon stuff. I can clean that up if you wanted to merge this.)

[jamesamcl]

Thanks for this. Shame the PR hasn't been merged but I'm using your fork for now.

[McPo]

@iriscouch is this likely to be merged?