&mut self in HttpService

[jonahromero]

Since service::Service was updated to use &self, is there any reason to keep HttpService::call as taking &mut self? It seems like a needless restriction when it's only being used to invoke an inner service::Service call.

[seanmonstar]

Hm, no, I think that was just an oversight. There isn't much value in the two traits being separate anymore. But I don't think we can remove it entirely, since people could have used them in bounds...