Honor the Host header in addHeaders #4
Description
When the Host header is provided it seems to be correctly processed by https://github.com/gobs/httpclient/blob/master/httpclient.go#L462 , but as the Host attribute of the request object was already set by that point in https://github.com/gobs/httpclient/blob/master/httpclient.go#L541 (the HttpClient.Host attribute is never set by the way) the Host header is ignored. It seems the correct solution would be have a special case for the Host header and set the Host attribute from the request accordingly.