Quoting from the splitString docstring:
NOTE: this function is not performant and should never be used.
This replaces trivial uses of splitString for splitting version
strings with the (potentially builtin) splitVersion.
- Use buildRebar3 instead of mkDerivation, obviating the need for setup-hook.sh
- Manually build proper and patch rebar.config s.t. it doesn't try to fetch it
- Set checkTarget = "travis" and actually run the tests
