changes:
  - implemented higher-order implications using a whole-program transformation
  - implemented subsumptions
  - created `semante.pipeline.test` package; from now on, only tests in
    this package will be run during compilation; it is therefore of the
    highest priority to port all existing tests to this package (and
    using the new format)

todo:
  - update the createtestcase function to create test cases in the new format