Http features

The `writeHead` method didn't take the arguments for status text and headers, so I added those.
Also changed the header names to be lower-case since that's how node core does it.

Oh right, and there's also the getDebugData function to get it all back since it's not usually a good idea to poke at the prefixed implementation details of an object.

I can change some of this if that's not how it's supposed to work here.