Extend the "list-t" dependency
Restrict the "either" dependency
Reorganize tests, use "doctest"
Migrate from HTF to Hspec
Merge branch 'master' into issue/16

* master:
  Migrate from HTF to Hspec
  Reorganize tests, use "doctest"
  Restrict the "either" dependency
  Extend the "list-t" dependency

Conflicts:
	tests/Main.hs