TODO

To make a release:
* Run build-all script.
* Bump version number in cabal file and in source-repository link.
* Tag git repo.

Koen's old TODO (trimmed):
* consider adding all QuickCheck1 flags (in particular: printing the number of test cases)
* remove unnecessary incompatibilities with QuickCheck1
* find consistent good names for functions (especially primed function names and callbacks)
* add more callback functions
* implement pre-test callbacks (add these as a top-level flag)
* find a good principle to decide what to export and what not
* decide what to export in Test.QuickCheck
* consider introducing special wrapper modules for certain extensions (such as callbacks)
* Deriving arbitrary, coarbitrary, shrink

More recently:
* Unify CoArbitrary and FunArbitrary?
* Make the testing loop more modular, and provide combinators for
  controlling when to stop testing, how to vary size, etc.
* Some general way of recording information inside a property.
* Replace 'promote' with 'delay :: Gen (Gen a -> a)'.
* Add the 'infinite' combinator and use it to experiment with e.g.
  partial generators, sized-based generators.
* Reformat things---some lines are 120 characters long!!!
* Add exception field to Test.Result. Maybe split Property.Result
  into two parts, environment and result, so that we can include
  Property.Result in Test.Result.
* Perhaps make Gen (Rose a) a first-class thing (maybe for internal
  use only).