Fix ci

[saep]

The CI builds started to keep failing...
The blog post here may make things easier: https://chshersh.github.io/posts/2019-02-25-haskell-travis

[saep]

The stack portion of the configuration works. The culprit for the cabal-based one seems to fail, because it cannot execute hspec-discover:

ghc: could not execute: hspec-discover

I personally don't really want to setup up a virtual machine to figure this out, so I'll be content with stack working.