Maybe add an example of how to use hyper client to download file?

This is a use case I am currently trying to use hyper for, and so far, so good I have not been able to figure how to do that out.

It would be a nice addition to the examples to include this :)

The basic client guide shows fetching a page and writing it to stdout. To save a file, the only thing you would change is to use tokio::fs::File instead of stdout.