Put all HTTP responses in the same window

I thought the workflow of creating a new window for each HTTP response makes it difficult to fiddle around with your request, since you have to keep going back and forth between the newly popped up response window and your request.

This pull request makes it so that all HTTP responses get put into the same "http response" window.

For people who want to keep the old way, it may be sensible to add a setting to allow toggling between the two. I don't mind updating the pull request with this feature if there's a lot of interest.

Sorry if the code isn't very "Pythonic", I'm not a Python guy :)