Needs more work on the error handling...

Needs more work on the errors

These warnings are false positives.

Encountered weird errors in CI with QuickCheck:

    view-shape:
      *** Failed! (after 1 test):
      Exception while generating shrink-list:
        Test.QuickCheck.resize: negative size
        CallStack (from HasCallStack):
          error, called at src/Test/QuickCheck/Gen.hs:135:22 in QuickCheck-2.14.2-0c
      Exception thrown while showing test case:
        Test.QuickCheck.resize: negative size
        CallStack (from HasCallStack):
          error, called at src/Test/QuickCheck/Gen.hs:135:22 in QuickCheck-2.14.2-0c

Later commits will port the remainder of the view tests; this commit is a
minimal switch which compiles, passes tests, and shows the feasibility of using
Hedgehog.

Unfortunately, both libraries for creating Hedgehog generators from Generic
instances turned out to be unsuitable.

- hedgehog-generic didn't work for modern GHC
- hedgehog-gen needed *all* the datatypes involved to be Generic, which e.g.,
  Alignment is not.