Test project / package after hypothetical package update

[czeildi]

Related to #31 and also the following comment of @noamross in #35

If you want to do live testing of a package, like seeing what system files/folders it modifies, I'm working on a Dockerized setup for our standard package tests: https://github.com/noamross/launchboat, so one could run tests in an isolated environment before installing.

Before updating a dependency to the newest version see which tests would break.

I can imagine this as a service (or maybe Rhub can already do this??) or a local version with Docker ensuring a separate environment.