Document native apps in place of 'Quickstart Terminal'

[cboettig]

The native apps Docker now provides for Mac and Windows avoid the whole need for Quickstart Terminal and the cumbersome docker-machine calls to get the ip. The whole thing works basically as it does on linux, just have the docker service running in the background and you can access docker through any terminal. The RStudio session is available directly from localhost:8787 (or whatever port you bind), no need to look up ips.

[pgensler]

Yes, this needs to be updated. With Docker4Mac(not sure of the version), there is no need to map docker-machine ip:<port> to connect, or whatever IP was given in Docker Quickstart Terminal. Instead, you only need localhost to connect.
https://store.docker.com/editions/community/docker-ce-desktop-mac