Fix custom request handler to work with other request methods (put, post, etc)

The custom handler implementation was only partially finished. When creating a custom handler such as:

var req = request.defaults({}, customHandler);

Only req(), req.get(), req.del() would use the custom handler. req.put(), req.post(), req.patch(), and req.head() would not. This fixes the problem using the same solution that existed, only filling in the other methods that were missed.