Consider directly using http crate types over hyper re-exports

For the *http* crate types `Request`, `Response`, `HeaderMap`, etc, while these types are also re-exported by *hyper*, I think the *http* crate docs are better as a whole, and its less cognitive burden to reference these types directly, in your top level usage example and code. The same argument could be made for the *futures* and *tokio* crate types, though *http* was the first I noticed.

This said, I've developed some bias against broad use of re-exports, so I'd also appreciate hearing reasonable arguments for using those re-exports, and would encourage you to collect other opinions.