Convert from "old" bats to bats-core

[NicMcPhee]

It looks like the original bats project has been abandoned, the currently active one is bats-core. (See, for example, the bats-core README and this issue on the original bats repo.

Given this, we should probably move the lab over from bats to bats-core, and make any necessary updates to these Practicum labs.

[NicMcPhee]

Following the git submodule approach recommend by the bats-core folks will require that every time a student clones the repo they will need to do:

• git submodule init
• git submodule update

to load up the dependencies.

Alternatively, and simpler, git checkout --recurse-submodules will do all this in one step.

[NicMcPhee]

Closed by #12