Use `baseUrl` instead of `host` and `path-prefix`

[kyaido]

Hi.

I'm using this github-changes on GitHub Enterprise.
But after update to v2.0.2, http request fails.

It seems that the @octokit/rest update now uses baseUrl instead of host and path-prefix.
https://github.com/octokit/rest.js/pull/807/files

Can you fix it?