Removed the copy/paste code, moved it into a reusable function that can
be called from the `local_setup` function as needed. Also simplified the
handling of the $HOME variable since @rico-chet provided a better way of
doing this.
Can't use the official v0.4.0 release, since our tests rely on a change
that was made after the release of v0.4.0.
This code currently uses an unversioned commit of the bats-core repo, we
will switch to a supported version once it has been released, e.g.
v0.4.1.
