[Request for feedback] HTTP client changes

I added some convenience methods to the existing http client module. The problem I see at the moment is that cookies (and when it will implemented, authentication parameters) are not persisted between requests.
So my proposal for what to do next is to add an `<http-client>` object (Python's Requests calls it `Session` but I think it's confusing) to do that, this object has all the http methods that when called change its state (e.g. they change its cookies). The current http methods will be changed to just create and http-client object and call the corresponding method on it.

The tests also need some love, this are just to see if what I wrote was working. 

Also I ask you a favor, if you have a linux machine can you run the http-client tests to see if they work? On mine they fail (IIRC for `socket error 11`) and I can't debug it at the moment because it's 50Km away.

Comments are very welcome because this is the first Dylan code I wrote.