Fixed headers

[innolabeveris]

I've corrected the request headers passing to the proxied url plus some gotchas.

[imjacobclark]

Thanks for the pull request! I've added a few comments to the diff, if you could take a look over them I'd be happy to re-review this, test it out and hopefully get it merged in!

Nice work.

[mrmx]

I've commited a new patch related to your suggestions here.

[imjacobclark]

@mrmx @innolabeveris I intent to merge this shortly, sorry for the delay, I have been adding a few unit tests and other refactoring, should land this week!