Figure out hyper::Error Display including source chain

[seanmonstar]

The current Display output of Error doesn't match what many people think it should, namely that it prints the error chain. We need to either:

• Change hyper::Error to not print the source as well.
• Influence the errors-wg to allow printing the chain in Display, like proposed in https://github.com/seanmonstar/errors/issues/1.

[seanmonstar]

I filed a proposal for the working group: https://github.com/rust-lang/project-error-handling/issues/53

[seanmonstar]

There hasn't been any progress on the proposal in the working group. To move forward, we can update hyper to format the way many in the ecosystem expect it to. If something better ever gets proposed and accepted, we can do that then.